Enclosing the entire cockpit of a CD25 in a ‘camper back’ enclosure of ‘clear plastic’ (ie Isinglass, Stratoglas etc) may not be your best alternative. It can result in an aquarium feeling, is VERY expensive, and it’s very hard to store as you can’t fold it, shouldn’t roll it tight, etc etc etc.
Your local climate matters. In Florida, we chose a Phifertex enclosure that zips to the ten year old King-made bimini, pics in the album. It gives 90% privacy, 50% wind reduction and reduces rain intrusion by 80% and can be folded tight and small. It has seven independent sections so you can put up just one or all depending on sun wind and rain direction, with three boarding sections including from the swim step.
Before investing, we would encourage you to talk to other CD25 owners in your area about all your options. And perhaps live with your current bimini for a few seasons to best determine what you really are looking for.
The opposite of what John did, is we used ShelterRite PVC/Dacron Scrim fabric to make our curtains, attached to Bimini with common Sense turn button fasteners. It was cheap, and totally water tight. But it will roll up, and bulky to store. We glued all seams, and glued the clear (cheap stuff) to the ShelterRite. All of the material was from Sail Rite. We used HH66 pac glue.