V berth mattress - We read in sailboat forums about the Spa Sensations memory foam mattress from Wal-Mart. We got the 8" Spa Sensatins Memory Foam Mattress for $260 (now $199). We measured the dimensions of the v-berth, then drew it on the mattress. He cut the mattress with an electric bread knife which was easy and didn't tear it.
We live over 90% on solar power and did on our previous boat, too. It's fairly easy on nice days in the middle of summer, but we do okay even on partially cloudy short winter days with just a little extra effort.