The Kawasaki 750 H2 triple ran a 1.85"wide rim with a 3.25 x 19 front, and a 2.15" wide rim with a 4.00 x 18 rear. Felt like driving on liquid snot. Was called the Widow Maker. I rode a CB 450 for years with 2.00" wide rims front and back with an Inoue 3.50 x18 front and an Inoue 4.00 x 18 back. Had to push the bars to get it off the vertical, then it would fall into the turn. Was very predictable. The flexi flyer frame was more of a problem than the fudging on the tire/rim size. My point, horsepower, frame, frame geometry, rider skill level and handling preferences all go into what works for you. My mentor said everything is a compromise in engineering. Taught me to take out the compromises that didn't work for me, make the ones that do. 4.00 inoue rear with a 3.25 ribbed front felt the best but pushed the front end much sooner than running the 3.50. My working hypothesis from 40 plus years ago.
Ran tubes for smaller cross section tires, adjusted tire air pressure to get the wear pattern I wanted. Made the tire feel as if it was on a wider rim. My opinion.