2008 Prophet with conventional Fox fork and external lower head bearing assy with approx. 11mm stack height.

Can someone tell me what is the MAX insertion depth for the lower bearing cup is in this steering head without me pulling it apart?

Externally it's got a straight section about 10mm in height before tapering into a little bit more narrow profile of the steering head. Is it only that 10mm section or internally is it nice and straight through so I can sink a deeper cup into it?