Hi, i drilled new holes 8,5 cm back, took a small allen key to remove the styro foam, put epoxy in and redrilled.
Not a big problem, just make sure to use slow epoxy that doesn´t get too hot while it hardens.
Rode it for 2 years and liked it a lot.
Then i discovered that it is more fun to ride the 633 with smaller stabilizers, currently i like the 325.
So at the moment the mast ist back in the original holes and will stay there. the position is just right for 330 and 325, but also for 420-
Please try a smaller stab first, this may very likely save you quite a bit of drilling....