Attach a Tempress Bench Seat to an aluminum lid?

[bigdogg1]

I have a Tempress bench seat (1/2" thick polyethylene plastic base) that I would like to attach to the lid of an aluminum storage box. The dimensions of the lid are just inside the dimensions of the bench bottom so it fits well. My issue is that the Tempress bench is made entirely without any place to attach hardware to the bottom and the seat foam cannot be easily removed to access the polyethylene. I am considering tapping Helicoil thread inserts into the base and bolting from the bottom of the lid into the helicoils. They are not really designed for use in plastic but are the best I can find. Any thoughts or alternate ideas of how to best attach the bench would be appreciate. Thanks.

 

[gunnerlove]

I was going to glue and rivet aluminum angles to the plastic base. If you did the same with 1/4" aluminum plates you could tap the plates. It would not surprise me if most people velcro them in place.