When did you send this originally?
Somehow I missed it last year, but I had a new heart valve installed last August, so
maybe it was during the time I was in the hospital.
Anyway, on your Apollo, which is very similar to a formula board (it's ISAF certified for formula racing) yes, moving the mast foot all the way forward can increase your upwind angle and VMG.
Exactly why, I have never been able to figure out, and while it has never worked for me, at my weight on my rigs and formula boards (I think an 11.0 m2 Retro or 10.4 m2 Sailworks NX are as large as I've ever tried to sail/race with) I know it works for all the formula pro sailors.
It might be as WMarker suggests.
In fact that really may be why it works.
I know that for a 75 kg sailor like me, even on Formulas and Apollos, I tend to run the mast foot much further back as this frees up the board and I do not have the weight
(might be technique or stance perhaps) to make a 100 cm wide board plane freely with the mast foot all the way forward.
For me, putting the mast foot up there just "sticks" the board, and makes it ride very hard over the chop at a somewhat slower speed than I can achieve with the mast foot further back.
But, as WMarker suggests, if you move the mast foot forward, you would be moving the CE of the rig forward as well and then you would need to rake the rig further back and probably shorten your harness lines and raise your boom to compensate for the additional rake angle to balance with the CLR of your big fin.
Hope this helps,