anyone upsized their tires to below (my previous BMW R1200 GS MY2016 have that size as OEM)
Front —> 120/70R19 (OEM YAMAHA S10 front 110/80R19)
Rear —> 170/60R17 (OEM YAMAHA S10 Rear 150/70R17)
The only comment I can make is to remember the TCS compares front and rear wheel speed to determine if the TCS needs to be activated.
If you make a change of tire size it will affect the front to rear ratio and at some point you may start to get TCS activation because of this. I can't say how big a difference will cause it to start, but it is something to think about when considering a change in tire size front or rear.
I would look up tire circumferences first and make a few calculations to see if the change you are planning will change the ratio very much. You can always switch to TCS-2 if it acts up or turn it off completely to bypass this issue if it becomes a problem.
All tires are different even though they might have the same size stamped on them. So there is for sure a good buffer put into the programming by Yamaha. What % change is needed for the issue to start is hard to say without being able to read the code.
There is not a lot of room under the front fender so check diameter to make sure you have room and don't get tire rub on the fender.