My buddy and I (he is 85 and now just builds and I fly) are on our 24th twin. We have tried various engines to date and, although they run perfectly well in our single engine planes, they tend to not be reliable in twins. Just about all our twins now have OS engines in them. I have yanked GMS, Thunder Tiger and Magnum engines for OS in several twins (.25FX, .46AX, .65LA). They are more expensive, but to me as the pilot, I am more than willing to spend the extra amount for the reliability.

OS .25LAs are good for basic flying. OS .32FXs will give more speed. OS .40LAs will also be powerful and probably the best choice. As I recall, the tanks are only 3.5 ounces and there is no way to install larger ones.

I do have a TwinStar. It does fly like a trainer and will do basic aerobatics. The control surfaces are fairly small. The most disagreeable thing about the plane is the covering. First the trim peels off, then the rest of the covering starts. I ironed during construction and I ironed after flights to no avail. I finally recovered the outer wings and installed larger ailerons. The nacelles are now peeling. I have it on floats with GMS .32s which, on a rare occasion, will give me a flight where I can land with both engines running.