If you're looking to buy that 6'10 just keep in mind it aint gonna ride like that whip at all. You may get it at a good price but it may not work for you. If you want the whip toi paddle better and float bbetter during the wetsuit season you may need to take it to a shaper. You can copy the plan shape, bump it out an 1/8, hide an 1/8 on the stringer buy doming the deck lower the entry rocker, keep the same rails but hold the thickness out to them, and BAM! You've got the whip but floats and gets into waves easier,spent $100 more but got the board you wanted and know works for you. That's just my $.02. Keep surfing, all the tinkering... all work andno play makes jack a dull boy!
Don't listen to people that tell you a board is to long. I have a 6'10 that has less float than a 6'2 beacause it has thinner rails and more rocker plus deeper concaves. It's all about Volume. If the wetsuit is holding you back you need to incease your volume to increase your float. If you have a shape you like go a little wider, a little thicker and even a little longer than your normal shortboard for some extra float. I have a 6'8 fish I ride alot in the winter just because its full of volume and gets out easy. If you think more volume means less mobile thats not true either. On my larger sticks I use a double wing cut down on the tail and its very responsive. Get a custom board and the shaper will work with you so you get exactly what you want!