Well, putting the mast foot all the way forward on a Carve 111 is about the same as dropping the anchor.
No wonder you can't get the C111 going.
For a 7.5 m2 rig, I'd suggest starting with the mast foot about 3/4 of the way back and maybe you will end up with it even a little further back than that.
I hope you aren't putting the mast foot all the way forward on your F-Type, as that would effectively kill alot of your performance on that board as well.
What led you to put the mast foot all the way forward...?
The only boards that need to be trimmed all the way forward are older formula boards with 10.0-12.5 rigs.
Virtually all other boards sail much more freely with the mast foot further back (sailor weight and sail size can have a small impact here).
Sounds like you've been trying to get the Carve 111 going, but left the emergency brake on.
15 knots....85 Kg. sailor weight....Carve 111.... you should be off on a plane with a couple of pumps.
Try and find a 42 cm vertical fin. This will help alot with early planing on the C-111.
If your back foot is dragging when you go for the footstrap, you don't have enough speed yet.
I think you still have a tendency to move back too soon and go for the rear footstrap way to early.
Let to board get up onto a plane before you even think about putting your back foot in.
Perhaps your board is "tail dragging" to some degree and this just makes getting on plane even harder.
It seems that you have a bit more to learn about fore and aft trim.
You do need to progressively move back, but only enough to get the nose up slightly to get the planing surfaces at the optimum angle to promote early planing.
Then you head off slightly, pump a bit and the board begins to light up.
At this point you can have your front foot in the front strap, but your back foot will be
in the center of the board and in front of the rear footstraps (how far in front I cannot tell you, but it will be somewhere between midway between the front and back straps, and the front of the back straps.
Once you find the "secret spot" the board will plane off easily and then you can gain some more speed and get it fully planing.
Then think about getting into the back strap.
If you move back too soon or too much, you just about eliminate any chance that your board will plane.
Combine this with pushing the nose down and making the board "plow" due to the mast foot being too far forward and you have the perfect recipe for making a easy to plane board into a very difficult to plane board.
Hope this helps,