It will run fine on the 15% nitro. You just get a little more power when you go with more nitro. More important is to make sure you have 20% lube with the YS or the Saito. These 4-strokes do very well with more lube. They run cooler and last longer. Can you get fuel that has 20% lube? If not can you get synthetic oil in pints or quarts? You must live outside Madison if you can't get high nitro fuel. That city probably has a ton of hobby shops. I live in Milwaukee.

BTW, how much does the Flip weigh?