Consumeratlarge - No, rivet nuts are not "blind" rivets. When installed, they leave you with threaded through-hole, so the length of the bolt is not crucial. Check
mcmastercarr.com to see how it looks. It was the only place where I could find stainless rivet nuts with 1/4" thread. Not cheap. You will also need Wrench-Drive Rivet Nut Installation Tool tool, costs about $30 at the same McMaster.
Or just put a pin through, forget the rivet nut. I installed rivet nuts (and secure pin-in-hex bolts) because of theft problem is Mexico, but panels prices have dropped since then, I doubt stealing it from the roof is worth the efforts.
My aluminum angles are not very long, 6". They don't distribute the panel weight, but rather the stress of anchor screws in 5/8" particle board.
I tried to hit the rafters whenever possible, but locating rafters is a pain, and it's not possible to have all the screws in rafters. So the angle has to be at least 2" wide, preferably 3 or 4", to drive 4 or 5 short screws where there is no rafter. 4" wide angle @6" length allows to drive 5 or 6 screws in corners and center, if you have to. For a flat install that will never be tilted, I think 4 screws per bracket is adequate. I got all my aluminum from
http://www.onlinemetals.com - all kinds of angles, all sizes, like 3x3, 3x4, 4x4 - whatever you need. They will cut it for you into 6" pieces for a nominal price, though a hack saw isn't difficult to use either.
Westend is using VERY long aluminum angles, and they indeed distribute all the weight and stress over wider area. I think his roof is different, so a different design was needed. Besides, he is tilting his panels - not sure how often ;) - so there is more stress.
I painted my aluminum brackets with Rustoleum paint, and don't see corrosion problems so far. Electrochemical corrosion of dissimilar metals (like stainless screw in aluminum bracket) requires wet contact. With screw heads buried in sealant, there is no wet contact. It will take a long time for my 1/4" thick aluminum brackets to corrode, I suspect they will outlast me and my trailer.
OP - one of the first answers, somewhere on the very 1st page, has the link titled "Various Installs". And other info that will be useful and necessary to you. In the "Installs" you will find that people have as little as 200W and as much as 900W, with different panels and controllers. It depends on your situation.
Happy holidays.
