Kirk, I thought about makin' them bigger too but, I just couldn't bring myself to cut into such a beautiful wing!
WM makes a 58mm wheel, (2 1/4"), that is a little wider than the tiny ones that come with the kit. The foam on the 58mms is just as hard as it is on the smaller ones.
BTW, I fly off of a somewhat rough grass field. It seems smooth enough until you drop a 8+# plane on it with dinky little wheels.
It isn't too pretty of a sight. Gets laughs though!
One more thing. Did you balance yours a little nose heavy? I did at first to be cautious then put a red painted flat disk of lead right under the rudder. Slightly tail heavy-SLIGHTLY mind you. This also helped keep the wood props from breaking.
Jazzy