CosmicR (./12):
Yes i think do the scroll straight after the Vblank starts. Yes tearing happens when you are updating an area at or after the same time as that horizontal line of pixels is being redrawn by the graphics chip. So for tall objects - like the scroll strips - make sure those are updated first. You only need to re-write character blocks in sprites that change. You can keep all the background sprite strips the same unless you are adding a new column of map tiles.

Thanks mate, will try that out..