The tires had better not stretch overnight if in mounted and without pressure in them. If so then think about what would happen when you do inflate them. While some folding tires are molded a tad smaller in bead diameter then steel beaded ones it's more the rim that determines tire mounting ease. A rim with little inside well won't allow a tire to gather slack when trying to get the last few inches of the bead over the sidewall. Some rims can be a real bear to mount all but the loosest fitting tires.


As to the tube question- Again the rim comes into play. a wider rim will have a larger internal volume (including tire) and be able to fit a slightly larger tube better then a narrow rim. Also most tubes are undersized to a degree. So if the 35/43 tube was only inflated enough to take a shape and not expand it would likely be smaller in cross section (width/height) then the 35 tire is. The tube will just expand inside the tire until the tire contains it and the ballooning up stops. So it is possible to install a 'wider" tube in a narrower labeled (and all these dimensions are only labels, not actual measurements) many times. Andy.