Self-tappers or self-snappers?? Help, need other options....

Ok, I mounted my rock rails last Friday before the Uwharrie run. I only landed on them once. Today I was jacking up the Jeep on the rock rails and here a series of snaps. I crawl underneath and I've snapped 4 of the 7 self-tappers at the frame. I used 1/4" self tappers, 7 per side. Will going to a 3/8" self-tapper work, or do I have to look at other options?? Please help me out here, I'm slightly frustrated since it took me so long to get them made and mounted. They are essentially a copy of Rocky Road's step rails. They have 5 1/4" bolts on the pinch seam also. Anyway, any ideas?? I really don't want to weld them on, so that's not an option. Thanks

Ary

When I built mine last month I used Steel rivet nuts.Ive got 7, 1/4-20's that go thru a 1"(.120 wall) that rests on the pinch seam and 6 1/4-20's that mount vai three legs the the unibody frame!So far it has worked out well,real stout and no loosening!

I used 3/8" lag bolts for mine. Haven't broken one yet.