Hi please can someone help.

I am looking to find a suitable aircraft/club for a male ab initio
with no prior experience.
However he is 6'4 and 231lbs (16.5 stone) though medium build. and I
am uncertain that he will be able to fit into the front of a K13 for
instruction.
Does anyone know of anyone of similar height and build that has learnt
to fly a glider and if so was it a K13/21 etc?

Thanks