no better expert of your questions than remi, he will be here with more credible answer than mine for sure. what i can add is my experience with the check of the new Phantom.
kona is a nice „freeride” kind of fun-raceboard, with fixed mastbase etc. lots of fun even for old school freestyle! Phantom is a course race oriented high tech board.
the Bat Wing bring a totally different dimension into the raceboarding feeling and a special advantage for heavy guys like never before! (i’m only 92 kg
) this board is kind of „2in1” raceboard. maximised tail width for reaching and down wind, where the tail width needed for early planning with closed in daggerboard and pulled back mast track. in the same time minimized the max width for upwind, to lift the board to the leeward rail for the best upwind angle and speed.
i competed with the AHD, F2, Fanatic Cat, Lechner and Mistral Equipe raceboards in the past. in early planning Lechner was the best by far, in strong wind the AHD (the old box railed), for allroud i liked the last Mistral Equipe the most. the new Phantom cover all of them plus the „old” Phantom too. the wider tail does not influence negatively the upwind ability, because no volume above the „wings” - thanks for the Bat Wing – and much earlier planning than any raceboard before, because the tail width.
to compare the old and new Phantom’s planning ability is a good example the formula tail width evolution.
in 2006 the Formula 160 was 100cm wide/ 78cm one foot off (width at 305 mm from the tail). the new Formula 167 wide is 100cm wide/ 90cm one foot off. that means more or less 15% increased the one foot off width of these formulas and developed extreme early planning in 6 years.
the „old” Phantom is 70cm wide/43cm one foot off, the new Phantom is 67cm wide/49cm one foot off. the one foot off width increased compare to last year Phantom more or less 15% - just like at formula (in 6 years).
as you see, in the early planning the total width of the board is not so relevant, compare to the „one foot off” width. so with the new Phantom you can planning some knots earlier than with the old one for sure! on top of that the thinner raceboard on rail is faster in upwind.
dont worry about the mast track, you will try it and you will love it in one day. you will get mastfoot with the board and the pin of it compatible with the pryde, severne, north etc. mast extension systems. if you want to use your mastfoot i think you can take out the mast track pin from the original mast foot and put into yours. i think maybe the north shox system is not good for the mast track, but remi can tell you.
i hope its help,