Lean bog, from my experience, feels like a surging almost, as if it's got enough fuel and then it doesn't. Rich bog, from my experience, is when it sounds like the engine is almost being choke, and when I give it full throttle while around 50-75%, it runs worse than if I very slowly ease up.
For the head, you sure I don't need the oring? I feel like it will have an air leak. I'm also going to put the smaller sprocket in, but from my experience, a properly running 2 stroke with a pipe and decently tuned carb would still hit some sort of powerband. Maybe I'm wrong? I don't feel like different gearing will magically bring out the powerband, but hey, worth a try.