I,m 6,4 and 88 kgs and cannot find anything on here about how a riders height can affect what dimensions of a board would be best [ i am mostly thinking of the width ] i,m on a 8,10 by 32 at the moment and its comfortable but would like to know are there any other tall guys out there and what size boards do they ride. Cheers
PS. age is 51.

6-5 and 102kg on a 8-8x28.5 123L Sunova Speeed most days and there are certainly bigger guys than me out there on smaller boards.

Height doesn't have a direct correlation to board size like weight does. It is a factor in your ability to balance, but some of that can be mitigated by practice and good form. Hard thing to quantify though.

Well I am at the other end of the scale.
The main benefit of being mid 5's is that we have a lower centre of gravity, and our bodies act as less of a sail.
The disadvantage of being short is that the paddle angle is more obvious making it more difficult to track straight on short wide boards. So if you are taller width of board should be less of an issue in terms of your paddle angle and ability to track straight. It also should help alleviate side strains and shoulder injuries from overreaching

I am 6'3 and 95 kg (but was 88 kg not long ago). Because we can't vary our height to see how it affects stability I guess it is hard to say definitively, but with a higher center of gravity I suspect that we need a more stable board. Sometimes when it is lumpy I will go into surf stance and crouch when turning around to paddle for a wave. I think it provides additional stability, greater power in the strokes, and better leverage to make a faster u-turn.

I'm 6'1" and 101kgs and ride the Sunova Acid 8'10" 115L and I'm a little bit older than you

Whatever your weight or height, there is the distance between front foot and back foot during your surfing stance. Have to be considered that back foot is used to fix fin(s) in the water and the front foot to turn that board around from or close of the widest point of the board with the front foot.
At same body weight, the first SUPer with short legs will need less distance between the tail and widest point of the board to torque it in a turn...second SUPer ( same weight than 1st) which is tall with long legs will get easily his front foot to close or past the widest point of the board making loose and maneuverable the whole drive of the board .
So to my opinion, you have to consider the leg opening of surfing stance you hold more than your height.