Oi. I am an idiot.
It is the FRONT derailleur that hits the tire when mounted at the 1.5 mm clearance over the chain ring that I wanted.
Arghhh .... why do people let me type things when they know i will get it all wrong? It's all everybody else's fault!
The rear derailleur is normal. The front derailleur touched the tire---more than touched it---until i fiddled with the mounting position.