harness line position for top speed

[nicolo.piccolomini]

hi,
to go as fast as possible i tend to place the harness lines slightly further back so that i sheet in as much as possible and the board is free to head downwind easily. however, i have a problem with this: since the harness lines are not positioned 'properly', my front hand works alot, almost as though i had no harness at all. this is a double problem as my forearm starts to feel the stress quite soon, as the conditions i sail in are between 30 and 40 knot winds with sails from 6.2 to 5.0 (which means i am VERY powered up!!) a year ago i had a wrist injury that prevented me to keep my right arm in strength, thus when my right hand is in front the fatigue and stress is doubled. is there any way to position my harness lines so that i still manage to keep my sail locked tight on the board, but relieve my front arm from excessive stress?
thank you