I'm going to have to agree with some of the other comments here, the question you should be asking is, "How is the Super Tigre G-50 Ringed Motor." If you want screaming performance on a Mid Star, a Super Tigre .50, an O.S. .50 SX, or a Magnum .52A XLS would be more logical choices. The Super Tigre G-75 should be for souping up a .60-sized airplane, not for breaking the sound barrier in a .40-sized airframe.

A Super Tigre G-75 would throw off the CG significantly, your extra power would be robbed by forcing you to add significant weight to the tail in order to balance the airframe. The extra wing loading that the heavier engine and the tail weight would cause would completely alter the Mid Star's glide characteristics and adversely affect the handling of the plane in many different ways. The extra power up front would also put additional stress on the plane's firewall and control linkages. A G-75 would lead to much shorter flight times as it would suck the fuel tank dry in half the time a .46 motor would.

All of this will add up to a poor handling plane with a short life expectancy. A more balanced approach will lead to a much more enjoyable flying experience. Any of the .50 sized two-strokes I mentioned previously should give your Mid Star outrageous performance if properly tuned and propped.