I decided to drill and tap directly into rails with #10-24 stainless flathead machine screws countersunk into the plastic panels. i ended up using (30) 1/2 long for most, (7) 1" on the bottom to stick through and maybe use later for a belly pan, and (11) 1" long to hold the cover on the top rails in addition to the (3) 1/4" screws in the front, and (2) on the rear rail that double to fasten the seatbelts .