Yes, I do understand the implications of a low Charisma (notice the picture). I was going to play him as a follower - a pawn to be played by others. He does what he is told when told by someone he respects. If you would like me to play Grai with a higher one, I'd be happy to - please subtract from Constitution.

As a side note: Looking at the averages in the PH is basing the scores off of a character with all 10's in the slots before adjustments are made.