That is how the genuine EVH Wolfgangs are done. FrankenWashie was looking at doing similar on one of his builds where you make a plate or bracket that sits in the bottom of the PUP cavity and allows height adjustment screws to do their stuff upside down. If the brackets are not made from high tensile steel the screws should tap a thread themselves as you screw them into a relatively softer metal.
Wish I come across that idea when I top loaded PUP's without rings on my EX-1.