Hi everyone. Don't know if this will help with surfgumby's answers but I have a 510 PN that I chose by volume. The litreage was very important in my chose of size and payed off. Before that I was test riding SP's 506 and 508 that a couple of mates have. I found that the 508 was to bouyant for me at 40 odd Lt's where the 506 (around 38Lts) was better. The board I was riding before the PN I bought, was around 29Lts 6'2" x 20" x 2 9/16 (unknown brand made in Japan) and was a bit of a brick and needed a nice size hollow wave to get going.
I'll try and post some pick's soon.