How to add storage to my new Crestliner Stick Steer

Just got my new Crestliner 1657 Outlook home yesterday and getting it ready to go. I knew before I bought it storage was going to be limited. I don't carry 14 rods and 10 tackle boxes, so not that big of a concern. But I would like to add storage large enough for my life jacket and cushion throw. I fish alone, so I already took out the rear seat. The storage box under the seat is 14" by 14", not large enough for the life jackets/cushion. Should I just get a simple ice chest and call it a day? I am trying to think of something simple that looks decent, no major modification.

I use my cooler for storage more than a cooler. I actually usually have a small one with drinks in the big one. I am in the process of converting the only real storage that I have into a battery box for the trolling motor.

Took a while but I found the perfect solution. Bought a $20 boat cargo net. Just installed it and works great. Holds the PFD's and since it's on the side, no floor space used.

Great solution! I modified two Lowes hinge-top storage containers to fit closer to the sides. Your idea has better drainage.