How much can i do with a 12 ft. Jon?

I just bought a 12' Tracker Topper last weekend and a 30lb trolling motor
and battery. With my friend and I and 4 rods and each of our tackle, an
anchor, and a small cooler the motor handles it fine and the boat seams
pretty good considering the load. How much more weight can I add to that
thing before I am testing it limits? I would like to put a platform between
the front and middle bench and then put some type of swivel seat on that
platform and then on the rear bench. How high do you think can go with the
swivel seats before the boat becomes to unstable and do you think it can
handle the weight of the wood for the platform? Any questions please ask,
thanks.