Nice boat!!
War Eagle sells a gun box in different lengths from about 30" to 6 feet that run down one side or the other. They are made for your boat, so they fit like they should with minimal work. They can be had with or without a cushion. They also have dry storage boxes, livewells, etc that you can use for storage. I have a "tool box" that I use for storage, it fits in the T-lock rail (gunwale channel), comes out in like 5 seconds with a wing nut.
That boat will float level as long as it's not overloaded. I have one (well mine's 15') and swamped it last year. Figured I'd lost it forever but it didn't sink. Just stayed about 4" or so above the surface.
I got a 548, and the only reason I got it instead of a 648 is that when you move up to 16', you are required to carry a fire extinguisher, throwable PFD, and a few other things that a 15' doesn't require by laws here.
Is yours 16" transom (short shaft). That's what I have; and that is the ONLY complaint I have out of mine. Sometimes when I'm loading on a busy weekend at the lake, water will wash over the back. If I were buying again, I'd buy a 21" and use a long shaft motor. IF (when) Yamaha builds the "new" 25hp motor, I may have War Eagle build up my transom and buy a new 20" motor. Luckily they're not very far from me. Lot of guys locally will knock War Eagle and they're all about Edge and Havoc boats since they're the latest and greatest (and supposedly the fastest....), and when I bought my boat I was aware that Edge was faster. After I looked at them, I decided that the war eagle was the best boat for my needs. I'm not a boat racer like the guys out at some of the public hunting lands are so I could care less about speed. I wanted a relaxing boat that serves multiple purposes and that is what I got. I use it on shallow trout waters, deep lakes, creeks, Arkansas River sometimes, in tight timber and wide open areas. I sold a fiberglass bass boat to buy this thing. The old bass boat was fast and fun but it was heavy, used a ton of fuel in comparison to my 25, seems like I spent $100 to go fishing every time I went, and even then I couldn't go to those shallow waters without dragging the rocky bottom.
https://www.pageturnpro.com/Arkansas-Business-Group/54076-War-Eagle-Boats/index.html#16