I just re-foamed all of the cushions on my 79 H30C. I bought 'firm' foam from an American,
online foam seller, which was cheaper than Sailrite.
The company is Ritchie Foam out of North Carolina, and is online at:
"
https://isellfoam.com/t/firm-seat-cushions". 704-663-2533
There are sellers out there, including Sailrite, that sell the white foam in 72" lengths.
My V berth is 76 inches long.
The "I Sell Foam" folks sell white, 24" X 80" foam, which you will need for both your V berth
and salon setees (if you do those as well).
Hope this helps.
G.