Greg Loehr nailed it. It's all there: mushy waves, huge fin, volume forward in the board, etc. Mucho respect for GL. (And it's glassed with RR.)
Incidentally, I was taking photos of my old Shaun Tompson which I was unable post but it totally matches Greg's description of Shawn as a surfer: front footed, fast and loose. It's about 5'10''. The volume is super far forward and a narrow tail that would fit nicely in a tube. Biggish single fin of course. When I was a kid learning to surf on it, the back 1/3 of the board was essentially unknown to me.
Haven't seen the fin you are using but some fins tend to be more 'grabby' than others.
The trailing edge of the fin on certain nose rding models has a distinct hook to it. It really does 'grab' the water and hold the tail down. If the fin is far back, it can be enough to suck the board back on the tail rocker. Have you tried moving the fin forward?
A smaller fin with a more vertical trailing edge moved up a bit would likely give yet another different ride.
Here are two examples - one with a fairly vertical trailing edge and one with the described hook. Which one is more like your own?
It's a lot like the one on the left. Same color too. But mines nicer: volan, Liddle template, shaped by Larry with minimal resin. The thing is sexy and flexy--and big.
So, putting Greg Loehr's theory to the test (so I thought), I took my new board out over the weekend.
Sets were overhead at a very low tide over a rock reef, etc. I paddled out between two peaks to just watch it for a sec, when a big set bubbled up on the horizon and landed me in perfect position. I went for it, dropped, stood, and--the board was totally gone. I don't know if it went in front of me or behind me or out the side. It was just gone and I was sent tumbling head over heels and done to the rocks. I paddled in right after that, went to the car, and got my 6'5'' thruster chip, which made for a very nice day of surfing.
Bottom line, I'm not ready to handle such a board in hollow, fast conditions. Whether the nose would have sucked down or not, I'll leave that question for another day. C
Thanks for trying, John. One thing I noticed in the pictures that I took (which I have not yet posted because of home computer problems) is that the nose on this board has a lot of volume forward. (It's amazing how much more obvious this is in photos!) I'm thinking that that, combined with a big fin, is the trouble. But intuitively, I would not have thought so. In my thrusters, I feel lift in the fins, not suck.