...... 3.25 vs 3.5 is probably not enough of a difference to matter terribly much.
Tire sizes aren't tire sizes anyway. Some manufactures have posted actual dimensions and there are some surprises. K70 3.25 have very close to the same outside diameter as the 3.5 and you're talkin' less than a cm width difference. The Avon AM26 3.25-19 are really close to the 100/90-19 in width but the 3.25 have a much greater o.d. than the 100/90. Go figure!