RE: Carve 121 set up
OK, now we are getting somewhere.
Your boom height sounds quite high to me.
Formula racers run booms that high, but for a narrower
board like the Carve 122 running the boom so high would seem
give exactly what you are experiencing, i.e. too much front foot
pressure and almost no back foot pressure.
I tried to look at a Gun Sails Groove, but since it's an older design I could only see that it's free ride wave type sail.
I'm a bit surprised that you have 2 sails spaced so closely together in size (0.6 m2).
I would think that for 11-16 knots you would want a larger rig (perhaps 7.5 m2) and for 20 knots you'd feel more comfortable on a 5.5 m2 rig on the '05 Carve 121.
Try lowering your boom, and try to sail your board flat (rail to rail) or slightly lee rail down by pulling up slightly with your front foot as you push across the top of the water (yes, try to push the tail away from you) with your back foot. This may serve to get the weight off your front foot.
Do you ever "spin out"? Probably not, as that woudl be a symptom of "pushing too hard" with your back leg, but it would be good for you to experience a few times as then you would know you are getting lots of pressure across the top of the board rather than trying to push down.
It sounds a bit like your high boom position may be holding your body in a stance that's a bit too erect, and your weight is going down onto the board, rather than being carried by the rig.
Try lowering your boom and trying to "lay out" over the water on the upwind side of your board a bit more. This should allow you to put your weight completely on the harness lines, and free up your feet and the back of the board.
Hope this helps,