|: How did you fasten the frames?
Very badly. I used bolts that went through the plastic of the frame and through the plate. The were fastened to the plate with locknuts. The problem was that the plastic that the Able frames were made of was too soft. After repeated use, the bolts pulled right through the plastic.
If I did it again, I'd fill the hollow inside of the frames with wood, and secure it there with screws penetrating from from side to side. Then, I'd attach that to the plates with either good solid screws or bolts.
However, I will never use inline frames again, as they really are not the right width for quads. In fact, I am thinking up a new design, as we type, for my next build that will be wider. I now manufacture my own UHMW plastic slider plates(as suggested to me by many on this site).