Make it 6x8 and thank me later.
How are you going to weatherproof it?
I built one out of 5mm luan, 2x2 framing and glassed it with 6oz fiberglass cloth and it's on it's 3rd season.
Window design is important, sliding windows allow you to crack them for ventilation to reduce fogging, flush shelf at window level wide enough for a gun rest and to protect seals, shelf above windows and no shelves below windows, wide enough for bag or back pack, floor needs to be sandwiched 3/4" plywood glued together(PL Premium) and sealed, pay attention to door design, my next one will have a framed RV door, windows only where needed, carpet for sound deadening on window shelf down to and including the floor
