Yeah I got that shock and it is ten times better then the stock one, as for the 10mm difference I have heard a bit of talk from members on here about that sort of thing. From what I have read it is a fairly big difference, 10mm there could be 30 or 40mm at the end of the swing arm.
yeah i did wounder that as it would change the geometry of things ill have to double check the length, the shock thats in there now has almost lost all it dampning you can push down on the back and it bounces up nearly lifting the wheel off the ground not exactly ideal
Put a block of wood thats 280mm where your shock was and see what the angle is. Just make sure its nothing too crazy, it will affect your chain adjustment and you will go through chain sliders otherwise.