Update: I installed a treats Puch sport touring head (to that I could free up my stock head that will fit my 40mm QT50. I'm really surprised how much it improved my power.
I think the difference could also relate to not updating the timing for the slightly different cylinder geometry.
I see the potential to deck the Polini cylinder and lose the gasket, but it's pulling hard enough that my attention is shifting to the clutch.
Thanks for all the help and guidance.