I am not a true speed sailor, but from my many years of experience, I find that the fastest point of sail is about 110-120 degrees off the wind. At this angle, I do not sheet in completely (sail in line with the board), but instead maybe 15-25 degrees off the board.
Regardless, my harness lines are balanced with equal pull on both front and back arms. If I have a good gust, then the back arm will have to work a little harder to keep the power on.
If you watch some of the record setting speed runs, the back hand is always working to control power, either sheeting in when possible to add power, or backing off if there is too much. I never see anyone with too much pull on the front hand.
I am sure others with more experience in "speed sailing" can help a little more.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.