I agree about the .26 four stroke being a little weak, for hardcore flying. Great for "Sunday Flying" though.
Unfortunately, if you like four strokes, you dont have a lot of options for "high performance" until your up there in size, and bucks.
I realize it is kind of a cop out, but what I do is bite the bullet and use a hot-NOT OVERSIZE 2 stroke in my wild stuff, and save the four strokers for the "regular performance" and scale or scale like stuff.
There is a trend (just read any of the magazines) to put a larger engine than the recommended range on your plane, this causes all kinds of other problems. ( Kind of like putting a V-8 in a Volkswagen- It goes like he-- and can be fun, but it isn't practical and has limited use). Hope this helps, and as usual, feel free to e-mail me to dicuss this, or any other airplane stuff at length.