Tonight I marked the spot for the ELT antenna hole using a string taped to the VS, drilled the dorsal fin, then temporarily removed the empennage to install the antenna nut. When that was all done I checked everything fits. All is well and I like it :-)
Later I'll make a slip-on fairing for the last 1.25" of antenna, but that can wait till I'm flying ... after all, I can probably live with 1/10th of a knot slower at 200kts, but there was no way I was leaving that massive base-loaded antenna out in the breeze!!