I’ll have to go against the grain and disagree with the previous posts on this one.
Some of my boards have a “B” after the serial number indicating that I stripped the bottom glass and reshaped that board. And I’ve done it sometimes for the same reasons you listed: too much foam- wrong rocker.
I also understand why some guys don’t want to do it. It’s working again on something you’ve already finished, and who wants to do that?
But a few of my boards were ALMOST there, shapingwise, except for some fine tuning that I was sure would change performance for the better. So I jumped in and did it. Luckily it paid off. The improvements were always worth doing. My two favorite boards are “B” boards.
If you want to strip the bottom and reshape, start by laying the board deck down and cut around the rail at approximately the new rocker line that you want. I use a diamond blade on a 4" Ryobi grinder motor. After you’ve cut all the way around the board, peel up the glass. If it starts to split the stringer, slice that area with a sharp chisel or razor blade. You’ll lose about 1 to 2mm of foam (1/16th inch or a little more). After that, shape it the way you want.
There are some limits to what you can do, because of the curve of the rails, but you can make significant changes.
Before you reglass, first sand down the resin on the rails, where the new glass lap will be, down to the old glass. When you reglass, you wrap the new glass around, laying it on the area you just sanded. It will make a good bond. Then hotcoat, sand, gloss, sand, and polish.
I hope I explained this so you can picture it. The main thing is that you can do it, and the result can be such that nobody will be able to tell that the board was reshaped. Good Luck! Doug