Hypothetical: I'm on the trail and I come upon this REALLY cute cycle gal. . .nice outfit. . .nice ride. . .pretty much all a 50+ could ask. Stunning, really. She's got a flat and no spare. Boyfriend has sallied forth to fetch the SUV and will arrive at a close by bailout at some time undefined for a rescue. [Boyfriend had no spare either, but that's another story my children.] She needs 26" Schrader; I've got 26" Presta. Fortunately [for her, alas], Sir White Knight is on his way so it's really moot. A Schrader-tube-to-Presta-rim won't work because of the too-tiny hole. Would a Presta-tube-to-Scrader-rim work. . .at least temporarily?