Any overall reduction in tongue height will remove the same height at the bridge, so the neck angle will need to be increased very slightly to compensate.

I'd probably try and rig up a belt sander (with a fine grit belt) clamped down on its side, and stick the edge of the neck to a flat piece of wood with double-sided tape to keep things angled correctly when offered up to the sander. You'd still need to be very careful and it would be very easy to overdo it.