Did you do all the fiberglass work and painting yourself? Looks nice.
I can't offer any real-life experience with your particular cabin, but looking at the picture... convert the port side to a single sleeper... add chocks the vertical wall on the port and stbd side then build a platform/board that sits on those chocks so that it's flush/level with the stbd side and fill with cushions.
FYI... you can find a 2-man tent that would fit in the cockpit - add a blow-up mattress and you're all set!
You won't find a pre-made template for Seadek, but you can purchase their template kit, make the template and send it to them. Then, once complete, get the "dry fit" to double check everything before you pull the trigger. It's peel and stick.