[Biff]

The suggested item is a T-nut, it looks like a T has a threaded center and some have small spikes that stick into the wood. You drill a hole in the 3/4" plywood and put them in before you cover the pool noodles. You are going to need a place on your frame to attach which if your bumper is to spec is 5" from the floor (2.5" space and half way up the 5" bumper). This method would leave you putting a bolts through the frame and into the T nuts. Hope this helps.