replacing back seat on glastron 1995 question on foam

[volleybiggs]

I am replacing the back seat of 1995 glastron. Those with the seats that cover the cooler make sure you open the seats and get the water out when done. Over the years the water has evaporated into the wood of the seat. So I decided to replace bench style seat. My question is the foam for the seat is crazy thin not like the foam on the front seats. I am guessing it is thin because everyone steps on it before getting in or because if the foam was thicker it would be more difficult to open the seat to get to cooler or storage spot? Any thoughts on this or has anyone done this? I am thinking of using thinking foam when I replace it thanks!