Personally I don't like using foam wheels. Even off of grass they get torn up quickly and start falling apart. The other problem I have with them is that they will soak up and fuel or exhaust residue that gets on them, and there is no way to get that back out. It's there for the life of the wheel. Yes, they are a bit lighter than rubber wheels, but on a glow powered plane it's usually very difficult to tell the difference between the two.

For your spinner it may be an issue of how you are using the starter. What usually causes that ring on the spinner is when your starter slips while starting the plane. The best thing you can do to avoid this is follow these steps. Rotate the prop clockwise (yes, opposite of the starting direction) until it hits compression. Firmly grasp your plane. Place the starter on the spinner and push firmly against the spinner. And I mean "firmly". You don't want it to slip. Activate the starter. If the starter slips immediately stop. The little bit of free play you get from turning the prop clockwise give the starter a little bit of room to get up to speed before it hits the first compression stroke. Also, a fresh charge on your starter battery will help give it the "omph" it needs to turn through the compression. Or even a bigger battery if it just doesn't have the bacon you need to start it.

One other cause of the starter slipping is if the engine is over primed. If too much fuel is in the engine then it will hydro-lock when you go to start it. If this is happening it's not going to matter how strong of a starter you have the engine is going to stop spinning and your starter will slip. To prevent this reduce the amount you are priming the engine prior to starting it.

Ken