Side bench/gun storage to withstand weight?

I’m modding a Jon boat, and wanting to add a side bench that will also act as gun storage. I’m trying to balance weight and sturdiness. I’m installing an aluminum sub floor, but thinking a matching aluminum side bench with storage might not be sturdy enough for some big boys. I,e. 250-300+ lbs.

Anyone have an suggestions? So far I have thought about using tubed aluminum framing with marine grade plywood for the siding and top of the bench. Would there be a better option, or any suggestions?

Thank you for any insight!

FWIW a friend put a used aluminum pickup truck tool box down the side of his Lund Alaskan model. He cut it in where the much smaller side storage compartment was. It was beefy, heavy duty and we shot from it, whilst setting up over decoys, as the height sitting was perfect. No pics though ….