I assembled the 20' tower in my pole building & transported it about a 1/2 mile away with my UTV trailer to my pond. All bolts must be assemble very loose to make the pieces all come together. Even then,I had to substitute some longer bolts for ones that weren't long enough. I rated 4 stars only because I felt the instructions could be better. Directions say that in some settings the method of anchoring the tower should be better then the 3 supplied 1" rods. I used three 8" X 4' Sonotubes. Drilled 1/2" holes in the supplied rods to add horizontal rebar pieces for additional hold in the concrete. Each tube required about 2 1/2 60# bags of mix. In order to center the tower legs over the Sonotubes the tower minus the mill had to be standing. I built a 2 X 4 base to rest the tower on while the concrete cured. Tower was also held in place by guide wires. After curing, I attached my two UTV winches on each side and slowly let the tower down on the hinged side. After attaching the mill, I did the reverse for erecting. Once up the mill starting spinning and producing air through the air stone. After one week the pond surface area around the stone cleared-up. I'm adding another 100' of weighted air line and an additional air stone to reach the other end of the pond.

Purchased mine kit off Craigslist, but my experiences should be relevant to other buyers.

First thing, instructions aren't that great. However, once you get going, it's just repetition until you get all done. I purchased additional flat washers and put washers on all the bolts on the tower. When assembling the blades and hub, make sure you leave everything "loose". By that, the nuts barely threaded on the bolts. You will need the slack to make the last connection between the braces to make the circle. I left mine loose, but not that loose. Had to go back and loosen 36 bolts on the fan bases. And almost as many on the cross braces. Once the circle was complete, then go back and tighten everything up.

I would recommend getting the hinges they offer for sale. It really helped me position my windmill and will help make taking it up and down a lot easier. I purchased the "small pond kit" which comes with the hinges, weighted air line, a bucket to hold your diffuser stone (any 5 gallon bucket will work) and a duck decoy to mark your air stone. I wish they offered some longer bolts to help attached the bottom stake brackets around the stake, but your local hardware store should have them. Having longer ones will help pull the brackets together around the stakes and/or hinges.

Also, they offer a bearing to make the windmill head turn easier on the tower. At $60 to $70 that seemed a bit expensive for ball bearings. I found a flange bearing on Amazon for $8. Just need something with a 2" inside diameter.

My 20' windmill is up and working. But it leaves a lot to be desired. In low wind conditions the fan will not turn into the wind until well above that needed to turn the fan. I see there is an expensive upgrade offered in the way of a real bearing as opposed to the provided flat washer. The performance of an otherwise quality product suffers greatly. I would have rated at five stars if it would rotate in low wind. "Edit 1/6/14 Found Amazon selling the OWS bearing for about 1/3 price elsewhere. Installed it two days ago and low wind turning much improved. If you live in area with low wind or wind frequently changes direction - I HIGHLY recommend the bearing as part of original installation. Taking tower down to add it later is not easy."
Following comments offered
A "Do Not Climb" sign. would be a good addition to the tower.
Also a solar powered LED on compressor to light up rotating fan at night. I added one as test and it gets a lot Wow's from our guests.
Not all info needed for installation is in or with installation manual. Example: only hinge installation says to drive stake with welded end up, dimensions for ground rod spacing is found elsewhere on OWS website - but not in installation manual.
Ground stake dimension doc says to leave 8 inches above base - installation manual says 2 - 3 inches above stake clamp brackets which are 3 1/2 for a total of six 1/2 inches? Hinges are the shortest above ground. If setting the pipes in concrete - set one hinge post first.
Had trouble getting tape and part number labels off - some still there. One or two had part number on tape which was helpful, one less to remove - would be nice if they would do that to all numbered parts.
Small impact driver suggested to tighten inside blade nuts - but not mentioned do/don't use on tower assembly where it would be a great time saver.
Installation manual wastes tremendous amount of toner/ink with black bands at top and bottom. Not good for a GREEN company. Maybe they could change online pdf doc's so owners will not waste ink. I printed two extra copies - one for notes and one for working outside. Keep orig. for files.
Very sad that prospective or new owners view a competitors assembly video. Wonder how many sales were lost? The installation video on OWS website is almost worthless for assembly content.
If concrete pilings or pad is planned, there are no dimensions provided for ground rod spacing in the installation manual. Be sure you find them (only for 20 foot tower) on OWS website.
Compressor specs are 3.0 to 4.5 cfm at 30 psi but they sell 20 psi rated pressure release valve?
Read complete installation manual at least two times before starting assembly. Instructions not great but doable.
How I did it:
Before securing stake clamps I leveled base with level. Then dropped plumb bob from top of tower. Way off. Went from what I thought was levet (using a 24 inch long level) to cutting an inch off one of the hinge stakes.
Precise stake locating and keeping vertical is difficult at best when setting them in concrete. I drilled stake size hole in small plywood squares then screwed squares to ends of 8' 2x with holes proper distance apart. Set one hinge post then used one of above to space second stake and then two for setting the third.
I cut out bottoms of old plastic buckets and set upside down over stake before filling with concrete. After concrete hardened I removed plastic. Cheap concrete form and with top of several inches above ground, tower base is protected from mowers and weed eaters. Tapered sides give professional look.
After cutting excess off of stakes I pushed a wad of paper in hole and down below cut edge, then filled hole with calk to keep water out of pipe.
Manual recommends adding 1/4" bolt thru ground stake brackets. I did and went one better. I also installed a bolt thru pipe (not hinge bracket) right at the curve/saddle of the hinge bracket ears.
Keeping grass cut inside tower base would be a difficult chore. I just put down weed blocker and covered with stones.

Windmill went together very easy. Instructions were good. Missing the bottom section when I received, but called and they sent out the parts right away.Parts all fit!

Trucking system that was to deliver was terrible. Wouldn't work with me on a time for delivery. Liftgate fee was to be $175.00. Wound up going to the depot and picking up myself.