In my Rotospun Frabil tub the ribs are pretty high. Even with the hi fax bolt cut off at the nut stuff slides around in the grooves in between. The nuts just rips things up.
It's to protect my tackle bag, camara case and such.
I also don't care for the seating in this rig so I use 6 gallon buckets and they rock in the grove closest to the side walls as its pretty wide. This fixed that as well.
I'll post you a pic but this is a very modest floor to say the least.