Ian
Yes...you can start the fill anytime in the bar...IF the setting for the fills CUE MODE it set to immdiate. Simple to change if needed. If CUE MODE is set to next bar, then no matter where you hit the fill key...it starts fresh on the next bar.

The only real bugaboo is that there is not a spcificfill for each VAR...so on some styles the fill sounds better on only some VARS vs Yamaha has a fill (autofill) on each VAR...but, if I understand correctly it always starts at the next bar, so you really don't have just a fill by itself that can be used anywhere in the bar.

Both have advantages and disadvantages IMHO.

Lee