Especially to boost your early planing, you can consider to use a race/slalom fin, of more upright angle. This will compromise the natural "carve" and freeride character a little, but for the critical semi-planing sessions, will still be your best option.
Hopefully you don't need to go super big/deep on a race fin- something 48-50 should be quite adequate to improve bottom end efficiency, whilst not quickly becoming unmanageable (or even just "not fun") once you're up to speed.
If you have friends or other riders near you, maybe try and borrow a fin or two in that range and try out before you make a decision about which to buy..
Cheers ~ Ian