My wife and I recently put new foam in the quarter berth (keeping the old cover) and made new covers for the v-berth (keeping the old foam).
A local foam shop did the cutting based on the old foam and glued on batting, all for the cost of the foam. We got the firmest foam, the most expensive of course. I'm looking foreward to a much better sleep on board this summer. About $550Cdn ($380US).
The v-berth covers were a project. Cutting all the seam stitching of the old covers to use as patterns takes ages. The fabric store had a good match of the original velour but it was very pricey. We went for an upholstery grade cloth on sale and a cheap navy nylon bottom. And reused the zippers. About $80Cdn. We used a Bernina 830, a good but almost 50 year old machine. It struggled at corners with 6 layers of cloth but otherwise soldiered though. My wife is pretty skilled but I learned a LOT.
Doing all the settee cushions is a big project no doubt. I think there are 9 on my E34. I don't think sunbrella is a good choice, it is expensive and not comfortable. Outdoor cushions yes use it. Sunbrella comes in good/better /best. Good is more comfortable for cushions. Best for covers for BBQ, outboard, winch, helm, etc. (use UV thread). These are great projects for the beginner. You can find sunbrella and nylon at thrift stores too and save a bundle. We scavenged scraps from an awning shop garbage bin. Perfect for patching repairs.
You should give it a try, and as Christian says the Sailrite will easily pay for itself.
Rob
Vancouver, BC
Original velour cushion cover (expensive)
Thrift store find, rip stop nylon, 5' x 6' for $6 (less 30 % senior's discount ;-)