i have an OMVL system it's been good, it's kind of hard to tune without a proper gas analyser, but i run a propane only system, with a variable venturi mixer, somewhat like an SU carb, it might run a bit lean according to the o2 sensor, the EGT hasn't been too high, so i don't know that melting engines is a problem, i ran mine hard for 9+ hours on several occasions and it didn't hurt anything when the engine was apart for the un-related oil pump fiasco.