Well, the Walbro carb will cure the sensitive needle issue, but the overheating could be a problem. Gasoline burns hotter than alcohol and the Magnum is designed with that in mind and has less cooling area. A little more oil will help, and a richer carb setting. If it persists, you might add some head shims to lower the compression. See how it goes. Really, if you are going to run an engine that needs a lot of oil anyway, you might just as well run straight methanol and oil. No advantage to "Gas/Glow" in that case really, except for the small percentage of nitro. Alcohol costs about the same as gas now anyway.

Good luck,
AV8TOR