After going back and having another look, I don't plan on putting rivetnuts and bolts along the top of each leg. I therefore don't need to undo the bolt you pictured. The kit came with eight rivetnuts per side. I have a 2014 so there are 4 in the bottom of the frame (facing down), two at the bottom of each leg. The front middle has the large hex bolt, and the top of the back legs are held on by re-purposing the KDSS and brake line attachments. I did have to gently pry the KDSS line away from the frame in order to slide in the rear leg. I don't plan on hanging off of rocks. I just need to be reminded I hit something, without doing major damage. I assume a rivetnut for every hole would have been provided, if required. I'll post if I run into any other issues. Highly likely I'm going to need another drill bit.....
Does anyone bother with sealing/painting the rivetnut holes to prevent future rust? Is one drain hole at the bottom the boxed frame enough to drain water? (provided it does not get clogged up? -- There appears to be numerous other holes to air out the inside of the frame. )