Does anyone know if you could fit a 26"x 2" tire on a Scwinn 24". Measurements show a clearance of 11mm or 7/16" but frame flex might rub the tire on the frame. Has anyone ever done this? If I were to buy a 26" uni w/out the rim, spokes and tire for ease of handling thru international airlines ( I got lots of spare 26" MTB rims and tires at home), what would be good for about $100 or less and where can I get one. Thanks 
Check out the Yuni. For less than $50, it is a deal that’s hard to beat:
Yes, the Schwinn frame will rub on a 26x2" tire. It will work fine until you start to pedal hard to get up a hill, then the frame will flex and the tire will start rubbing.
Back in the “old” days the Schwinn muni conversions were somewhat popular due to their availability and lack of availability of alternatives. They worked, but the frame flex caused the tire to rub when used with a 26" MTB wheel.
A much better alternative is the Yuni frame that Krashin’Kenny mentioned. I wish we had the Yuni frame back in the “old” days.