The top could be removed and that T fitting could hold a gauge while the pressure is being set...
Then the gauge could be removed and the extension and anti-vac installed in its place, protruding through a hole in the top once the pressure is trusted to be where it should... Just spit-balling the idea.

HI,
From datasheet of:
SIRAI ELETTROMECCANICA
www.sirai.com
www.emerson.com/asco



Also JAEGER CONTROLS on model PS-14, one of the best price-quality-dimensions pressure switches, recomended this connection.
Regards

Hey Zan
Deposit from tank should be no problem with Cremina original pressurestat connection point near the over pressure valve inlet and that U band is nice idea as it will bring adjustment screw up side for ease of adjustment