I also used a single large angle from home depot. Give the pro-seal extra time to set up just to be sure - I think I left it a week to 10 days. You'd be surprised how solid it feels with the pro-seal cured. After that I followed the instructions for riveting, back riveting every 10th rivet, then slowly filling in the gaps. I set each rivet just very lightly at first, then worked back and forth slowly setting them further. You will see there is a technique to slowly 'rolling' the back rivet set as you rivet to set the rivet into the dimple neatly. I finished them all off with the mushroom set on the factory head which created near-perfect shop heads.
I have screwed up a lot of other things, but I can say that using this method I ended up with a perfectly straight trailing edge!
Chris