Off at a tangent 110 front 150 rear is fine on a lightweight 250 - I have these on my Trackday VJ23
Phil, deciding for factory settings is always good. A bit more in detail, started a "study" on how tyre sizes front and back could influence turning and turn ease on a bike. This was inspired by a article by Mat Oxley i read some time ago. To keep it Short, and how i see it, for turning purposes, and only that, the front tyre should be widder then the back tyre, but this is not viable for obvious reasons, power goes to the back, so grip is necessary, etc etc etc.
The next best, and again only for turning ease purposes, would be the skinny the Better, and the closer possible sizes rear/front. Again, only my Humble opinion.
Not bugging this thread anymore with non relevant stuff, sorry. Just because i picked up on the tyre sizes on the Vins, that support my study or research... Right or wrong, purpose or coincidence, have No idea :-)