Insomnia induced ...
A few observations about racks -- racks on a medium height, medium length wagon. And use my thoughts only as my observations not the gospel.
I can't tell much about the anchors. I will note that you will probably need to get an 8mm tap to clean the overspray out of the threads. I'm going to tighten stainless bolts to 10 ftlbs. Interestingly, I found stainless fender washers but not of sufficient bore to allow the 8mm. My son and I found out how difficult it can be to drill 8 stainless fender washers.
Anyway, we're going to use the fender washers, split washers, and locktite.
I built all the feet/uprights/towers out of 1 1/2" square tubing with 1/8" walls (The same material as the frame.) on 3/8" 3"x5" plates. The footprints have a 5 deg. rake. So the feet have a 5 deg tilt to achieve square. The feet sit on a 1/4" poly plate and a heavy nylon cloth impregnated with pvc (known to me as material from a whitewater raft), on silicon directly on the metal.
A special note and note to self -- think things through. Thinking I was smart, I got my wife to assist in determining how tall the feet should be. (Since we live on a hill with a sloping drive we drove to the car wash with two ladders for flat ground. LOL) Anyway we measured and put up a wooden model in the middle. We didn't think about the fact that the rear of the van has more bow. Fortunately, I have enough clearance. In fact, I wanted stealth and the rack fairly close to the top of the van. However, to be truthful, it ended up being closer to the top (in the rear) than I would have dared.
Yes the frame is heavy and I think very sturdy.
I'm going to wet blanket the top and get some friends to help put up the frame on the feet and tack em up there. We'll then take it all down and I'll weld up the feet, finish one more section, make mounts for the corner lights, some sort of deck plan, fold down kayak towers, then paint it and be done. (excepting the ladder...)
A blurry photo of the deck (almost done).