:WELCOME:
Maintaining the structural integrity of that boat is a MUST. If whoever owned the boat previously removed bench seats or what-have-you that were instrumental in helping keep the structural support of that boat intact you MUST substitute with some sort of suitable bracing bracket. Otherwise, you risk the boat forming serious stress cracks & popping rivets (especially on choppy water at high speeds). Btw, I know some here will say "don't ever use treated lumber for the flooring in an aluminum boat" but, I'm not totally convinced. I've been told (& have done it myself successfully) that as long as you have an adequate barrier (aka good quality paint, bed liner, steel flex etc..) between the aluminum & the P.T.L, you'll be fine. In fact, some have said in the past that the rule of "no P.T.L in an aluminum boat" only really applies if you're using the boat in salt water (which apparently won't apply to you). But, you decide for yourself & good luck.