I was just shown a really good technique for securing the frame/speed rail fittings without drilling holes... at least in all the speed rails.
I built a standard double rail 4 bay frame. I used 90* speed rail fittings for the outside corners, and used Ts on the inner rails. I used Lo Pros for the bay cross bars, which I bolted.
Instead of drilling holes for the Ts and 90s, you can secure them with zip ties. You zip a loop on the 90 fitting, as well as the T fitting on the inner rail. You then link the loops with another zip tie. To really tighten everything up, get the zip ties from slipping or posing an entrapment risk, you take two extra zip ties and use them to secure the linking ziptie to the outer cross rail... if done right everything should be tight, snug, and won't slip anywhere.
I was a doubter, but this actually looks pretty bomber. If you use that with the set screws I think you have a solid frame.