Okay, I was confused. The OP was asking a basic question, but then there was the post about the flywheel not being worth it. That was from a different guy. The OP may not be turning 7200 rpms (I can't see him spinning more than about 6000 with stock valve springs). I will say that I love the flywheel. You're correct in saying that it didn't increase my power by much, but it did make it safe to spin the motor over 6000 rpms. After the rod and flywheel, you can go with monster cams, bigger valve heads, etc. If you're building a motor to race with the big guys, $100 is nothing. You may put that into the motor on a monthly basis if you're really racing.
I know there are other sites (I'm a member there as well) that think the OldMiniBikes guys are a little too uptight about the billet bits. I disagree. This site is packed full of knowledge that will help you build a monster engine. The owners simply ask that we give out our free advice safely. I can get behind that. I have kids. I know how valuable a fun-filled life can be. I value my safety, and the safety of those around me. If you prefer to disregard this request, that's your call. But giving unsafe advice may result in you not being invited back to play.
If $100 is too spend for you, there is always the PVL option.
Flywheel, Aluminum (Dyno PVL), Racing, 6.5 Clone & GX200 I don't know anything about these, but they are supposedly rated a lot higher than 10,000 rpms. Anybody producing that kind of power is probably running a real Honda block with reinforcement, and $100 is nothing for them.
Have fun, and be safe.