#1  Since I twist the ends of stitch wires together outside of the hull, the stitching is easier for me while the hull is upside down.  I level my building supports before final stitching/tightening to minimize any twist to the hull.  With the hull upside down it's easy to look at the seams to check for fair lines and adjust/add stitches as needed.  Use whatever method works for you.  Just don't be in a hurry; spend the time to loosen, tighten, adjust, shift, replace broken stitches, etc to get a fair hull.

#2  It is certainly easier to cut holes for inspection ports before the bulkheads are installed.  Measure twice, then cut and drill the holes needed.  Then clean up the edges (sand).

Thank you for the help. I did find it easier to get all the seams wired hull side up, then did some fine tuning after I flipped it and suspended the boat. Cam etogether really nicely! Thanks again.:)