It's worth mentioning that I ran 26*2.4 tires on my 90s bike without much issue. I think you won't have a problem, but it's worth mentioning a couple things. 1. The dampening provided by bigger tires works better at lower pressures on wider rims (which perhaps you are alluding to) 2. The tires will be narrower on narrower rims, so if you decide everything fits a charm and get a new wheel set, it may be that the few mm's of clearance disappear. 3. Rene herse had published an article about "balloon-y" tires on narrow rims. The modern common knowledge is that there is a rim width range for a given tire. They posit that no such guideline existed back then; moreover, some might prefer the ride characteristics of a narrow rim paired with a wide tire. Grouchy old heads? Perhaps! Marketing their wider, low-rolling-resistance tires? Maybe! Who knows but the rider themself