UPDATE
Okay. After fartin around and trying every trick in the book.... TA-DAAAAAAA!!!!!!
Nothing.
Still can't add ships to OP in shipedit. I've followed the tutorial and even loitered in some very old docs I had from the good old glory days of SFC II.
In a nutshell, I add the models to the proper folder, I open shipedit, loadup shiplist, create new ship, go through the UI and model selection routine, and then I fill in the blanks. Save. Fire up SFC: OP and try to start a singleplayer test skirmish... nothing happens. No new ship.
Anyone got any ideas about what I might be doing wrong? What are the really common rookie mistakes that I am probably making....