Are you guys calculating with the piston below the exhaust port or above? Cam.
The right way in my opinion and even almost the whole "twostroke-world" is when piston close exhaustport and start begin to compress.
(Look at Kawasaki manual:Low rpm/exhaust porttimes low(KIPS)/more compression)
High rpm/exhaust porttimes high(KIPS)/less compression
As always: just my 2 cent