I ended up in the exact same place, except, I was the idiot who created the board from a blank, and radiused it before I cut the taper... Mark's solution is how I handled it... successfully so far.

@adam I have access to a planer as well but I'm worried it would rip out at the fret slots On my three builds so far I've used Mark's pre radius slotted tapered fretboards so can't offer any hands...