Need help hanging e-track in trailer

Grit dog wrote:
actually, if you can give up the width, and need to hold significant weight or pullout, the idea of screwing boards (2x4) or strips of good 3/4 plywood (won't split or crack) to the wall studs, top to bottom, then attaching the E track to a thicker material (more screw threads) may be the best bet.

I got 1x4 boards to mount the etrack to. I made the mistake of getting too long self-tapping bolts, which ended up going through the skin of the trailer. Had to Dremel off the ends. The problem is that the "self-tapping" end of the screw was too long - almost 3/4". I tried using 2" self tapping initially, but since the tapping part was so long, it wasn't getting much hold on the beam. I believe that the beams are steel, because they were a ***** to drill though with the bolts, but I'm gonna bring a strong magnet and check. I've only put up one board so far. Once I put two holes in the trailer, I didn't want to risk putting in more. I'm on the fence whether to put some silicone caulk over the cutoff screw ends or actually removing them and attempting some kind of repair. This is a 8 year old cargo trailer, so I'm not trying to win any cosmetics awards.

I was thinking of Rivnuts, but I'm not sure what the structure is of what I'm screwing into. Rivnuts require some hollow space. I simply don't know if I have it.