Yes in theory, though at full rake the increased jib twist is helpful rather than otherwise and if it's really honking fiddling with jib car position is not likely to be helpful to boat speed.  I defer to the experts however

OK, I have read the on-line tuning guides and got a road map for setting up my rake and tension markers ready for a day playing with it in the wharehouse at WPNSA.  However, a bit confused on adjusting the jib car position as mast rakes... is it move the jib cars forward incrementally as mast rakes back to keep the slot shape the same?