by waikikikichan » Sun Jul 31, 2016 10:29 pm
Just get a 9'0". That's the official minimum size to be considered a longboard. Awhile back, all the Japanese were ordering 9'3" because that was what Joel Tudor was using. But Japanese aren't usually as tall or built like Joel, so that was a silly reason. For you, If you catch everything and anything on your 6'10" than a 9'0" will be easy. Walking wise, you still probably haven't learned to stall and cross-step yet, which is essential to a good noseride. I'm only 5'2". My best board is 8'8" which is not legal for competition, but it matches my "stride" / step length. When I walk on a 9'0" I always have to do a half step to get to the nose. It'a going to be hard to figure out right now your actual noseriding walking stride and where you end up on the nose. And that's why it's hard to recommend a exact length.
Another factor you might consider is if you can knee paddle a 9'0". If you can't then you might want to go longer ( and wider ).