re: ISO Aluminum plate ( Boat pictures added)

Just a few observations from my experience with this kind of project.

My brother has a SeaArk aluminum center console with screwed down aluminum floor plate. He lost some screws, so I called SeaArk to find out what they used and they said 410 stainless. I never really saw a lot of galvanic activity at the screw holes, just lost some from vibration.

Make sure your pilot bit is sized correctly or the screws will gall so bad you will break them off going in. I also think there is a lubricant you can use on the screws that will help. I've seen it used on aluminum conduit to prevent galling.

His deck plate is smooth plate but appears to be coated with a non skid bed liner like material. If you went that direction you could roll it on the top of the ribs too. Will hold down on the metal to metal contact and noise from vibration. Diamond plate is nice for the grip, but a pain to screw down. The raised grips may force you to put screws in spots that aren't ideal.

To echo someone's comment about the ribs cracking through the screw holes, I have see that happen a lot on lighter built boats. That SeaArk has really heavy ribs. If your boat has light weight ribs, I would be cautious. Good luck!