You will find that with the 120/90 height rear tire, the bike will lean a LOT more over the sidestand, making it pretty unstable. If you go with an 80-profile tire in the 110/80x18 and a corresponding 100/80x
1819 front, it will sit on the sidestand far better, not wanting to fall over when something is strapped onto the seat (like a knapsack).
(Fixed typo on front tire diameter.

)