Quote:

I think I just suss,d it out 270deg, one piston TDC the other piston bottom of the stroke 360deg, both pistons are both at TDC but only one is on compression stroke the same as the old pommy twins.



Your take on the 270 is a 180.
On a 270, one piston at TDC, the other halfway between TDC and BDC.
This link had been posted before, shows them pretty well:

web page

Contra todo mal, mezcal; contra todo bien, también