You can also take the blue collar off of the low speed and leave it off if you want. that's what I did with the one I have on my LT-40 beater plane. Sometimes the mass of the pin and collar seems to allow it to rotate with engine vibration, changing the mixture. It's not normal, but I've seen it happen. Once you take the collar off, you'll be left with a screw sticking out that you can adjust with a screw driver easily enough, and that will stay put on it's own more easily.

I left the flywheel on the one I have (which I bought used), and I don't notice that it's there. I run an APC 11x5, and I took the baffle out of the muffler for a little more power (and quite a bit more noise).

I've had 20+ students now with the .45 and .61 flavors of the Evolution engines in various trainers, and I've yet to see one that didn't run great. They even flip start really easily once you learn how they like to be primed (a bit richer than some other engines).

I do like the super tiger engines, but frankly, I think the evolution is better made, easier to tune, and more consistant out of the factory than the ST. YMMV of course, but given a choice, I'd go with the Evolution in any plane of mine.