Indiepath, well spotted, thanks. Yes removing the print seems to smooth it out on mine. I added the print as it looked a bit rough originally, but that was due to the dodgy MSPerFRame probably. Bit like quantum physics this, when I examine it (with Print) I change it (i.e. it becomes worse)! Anyway, I'm still considering adding in some compensation code and testing it (with print) and then taking print out and giving it to some users who experience jerky movement/scrolling to test.