won't be a problem, so long as you keep the tire brands the same*. that's how the 748 is. honestly, i don't like to see 120/60 on any ducati, as the wheels are too soft and bend easily on pot holes.
* note: tire brand matching isn't an issue if you've got chicken stripes... and maybe not even if you don't. it's when you're at a track and riding off the edges of the tires can mismatched profiles zap you.