I don't know what to tell you, it didn't take me any time to get used to Schecter's neck profiles after years of playing Ibanez, and the Loomis is generally slimmer from my understanding than the regular profile Schecter uses. Hell, I ordered my KxK's with the neck thickness of a Hellraiser
But for a solution, I'd just bear with it until you get the Rico, or try adjusting your technique slightly. Try holding the guitar up higher or lower, see if that alleviates the cramping. If you're cramping, there must be something you're doing wrong (for that guitar). I'm not saying you have bad technique or anything, just that a different neck profile will probably need slightly different technique. If you're set on a thin neck and don't want to change, I'm sure you could unload the Loomis here.