I don't think that is the way to look at it – shifting the mast foot doesn't help you plane any earlier on a wave board.
You could shift the footstraps forward if the tail is sinking too much or just lean forwards more. 'Pop' technique also helps you get up to speed.
But, really, a board planes easily if the sailor isn't too heavy for it. The Evo XTV70 IS an early planer, in terms of hull shape/rocker line, but is best suited for a sailor of 70kgs or less.
When you feel a board is slow to plane but your sail feels powerful enough then it's usually because you are on too small a board for the conditions – with the worse case scenario being when there is white water or an adverse current that is not helping water flow over the hull.
Some other Starboard waveboards – those with higher rocker, meant riding bigger waves – may seem relatively slow to plane but this is not the case with the Evo70s I have sailed (and I've had 4 of them, over the years).