Paul~
My approach is very similar to Dave's: a cowling (low dodger) and a lap canvas. I do not have great pictures of my Sneakbox - I last gunned it during my pre-digital camera years. I thatch up the lap canvas with pockets I sewed into it. It is fastened at its foot (to the back of the aft cockpit coaming) with snaps (I use Common Sense fasteners now). Because the cockpit is wide like yours, I have a broom handle sewn into a pocket up forward. Its ends drop into notched chocks inside either coaming. It is strong enough to support the gun, binoculars, etc but also just pops right out of the way when I sit up to shoot.
Here it is in gunning mode (BTW: Limit was 3 birds back then!)
Here are the chocks to hold the "broom handle":
On a newer vessel (DCE - digital camera era), I used just shock cord and thumb cleats to hold the upper end. The shock cord gives enough when I sit up to shoot.
The low cowling is for open water gunning.
Here it is in gunning mode - notice Common Sense fasteners at foot.
Here is the lap canvas rolled up- for picking up birds, decoys, travel, etc.
Dave: Thanks for the tip about the fibreglass rods at Tractor Supply. I once put Lucite rod in a dodger/cowling to stiffen it - it do not survive the first trip!
All the best,
SJS