If you go back further with the pup rout, make sure that you don't foul the PUP ring on the front of the Cone Cover.
It sounds as though your sound well was deeper to start with, which is good, how deep is the body at the edge? Mine measured up at 1.875" or thereabouts.
Does yours have the through holes for the PUP and the piezo pre drilled? Inquiring minds wish to know. Also how are your screen holes? are they actually circular or are they a bit iffy as well?