Ron, I have it well bolted to the concrete, 6" square footpads with 4 lags in each of the 8 legs. The pipe is 1-7/8" schedule 40 steel, so it can't flex more than an inch in any direction. It's 30'x16' and about 13' high, so lots of clearance if I park it on target.
I bought the fittings, tarp and bungies from creativeshelters.com. They have a design feature on the site that lets you create a "kit" that meets your desired shelter dimensions and configuration, then gives a diagram and cut list for the metal fence tubing that you will buy from a local fencing company. My local fence company cut each piece to exact size for me. There are many choices on the site for different tarps, and different configurations. The shelter I created is a 16' x 30', made with the largest/heaviest fittings/tubing (1 7/8"), with the medium gable peak (110 deg slope, 4" rise/foot), and the heaviest/most sunblocking gray tarp.