Generally a larger aspect ratio tire (taller sidewall) is a bit more tolerant of rim width, as the increased sidewall height allows more flexibility....however there are still limits.

Also - when you increase the height of a tire by going to a higher aspect ratio you increase not only the amount of weight, you also increase the inertia of the tire as a result of the larger radius, and you change the rpm/mph ratio.  This can significantly slow down the acceleration and braking of the motorcycle, and also inhibit the ability to change direction quickly.  You get a bike that is slower and harder to turn (which is certainly not something I want).

I am more interested/concerned about "performance,longevity, safety" than I am about the "cruiser" look.  When you install a tire that is wider than suggested for a certain rim width, you compromise the performance.  The tread contact patch with the road is affected.  A tire that is squeezed onto a narrow rim has a narrower contact patch and the handling can feel very "tippy" when going in a straight line........it can also do weird things to the handling in a curve.  Most modern tires have a design that provides a small contact patch in a straight line and a big contact patch when leaned over.......when you use the wrong size rim you have altered the way a tire works.  (Vintage and Cruiser type tires may not have the same tread contact patch as a modern sport touring or sport tire).

I have run a rear tire as narrow as 110/90 on the back of my Savage on a 2.50" wide rim, and it never lost traction and handled fine.  I am currently using a 130/70-18 tire on a 3.50" wide rear rim and a 90/90-18 on a 2.15" wide front rim.  This is the perfect setup for the curvy roads that I ride.  The bike is a little twitchy in a straight line with this small front tire but works just fine when leaned over.....a 19" front wheel may be more desirable for straight line stability.

Stuffing an overly wide or tall tire onto a Savage will affect your handling in a negative way - but if you just ride around town and don't drag pegs in the curves and aren't worried about the center of your tire wearing out quicker than it should......it is your bike and you can put whatever tire you want on there.

Has anyone had any experience with the portawalls then ???

What are some good alternatives to white walls then rather then switch tire sizes ??

Like I know the portawalls and can get a set for bout 100$ cdn, I’m in Canada lol.  But I have heard they fray or lift or don’t stay out of driving over 60mph.  
What about paints ? How well will the paints hold up ? I also have seen guys “sanding down” their sidewalls for paint to stick to them lol.  Personally I think that is not a good idea for what I have seen I would be worried about a blow out or tire failure then.  
Are there like decals or special stickers maybe to adhere to rubber that could be used ?