A few thoughts.......
I've got a early 1970's Sears 12' semi v. The boat has a 585lb capacity on it. As of now, my mod has the following things in it.........
15hp Johnson - 76lbs
Carpeted plywood front floor (angle aluminum frame underneath) - 25lbs
Carpeted plywood tops on both seats - 20lbs
Carpeted top on the bow to mount sonar/trolling motor - 10lbs
45lb MK Edge trolling motor - 30lbs
Misc fishing gear/sonar units/seats/other electronics - 75lbs
27 series battery and and lawn tractor battery - 75lbs
2 bank onboard charger - 10lbs
This all equals roughly 325lbs before I get in the boat. I'm about 225lbs myself. Just by myself, the boat is fine even in rough water. It was a bit scary, but I got stranded on a big lake 2 weeks ago when the wind picked up and I had to make a 2 mile run back in 3' rollers. The boat did fine. With that said, when I add another 200lb person to the boat, it gets a bit hairy. Safe on small waters, and places where you don't have to worry about any whitecaps or bigger....but to be honest it's really just a bit small of a boat for more than one 200ish lb person in the boat. It's also not very fast.........I get 18/19 mph alone in the boat, and 15ish with another 200lb person in the boat......it's definitely a wet ride with two people unless the lake is glass smooth.
One thing I'd suggest is to use angle aluminum for the framing for any decking or floors. It's MUCH lighter, you don't have to ever replace it, and it's MUCH easier to work with than wood. It literally took me maybe an hour to frame my front floor with aluminum, all I needed was a cutoff tool, drill, and a cheapo rivet gun.
Hope this helps!