I figured someone would have replied by now. I'm not a carb expert, but this is my learning on the subject. The main jet is the wide open throttle circuit. It actually works in conjunction with the needle taper and clip position, and starts opening up around the 1/4 throttle position to WOT. As throttle position increases and needle taper decreases, the orifice opens up more. You state different kinds of mains, do you mean different sizes, or did you get some pilots also?
What part of TX are you from? I'm from the West TX (Midland/Odessa are biggest towns in vacinity) area.
jets are for your fuel air mixture.the bigger the jet, the more fuel going into the cylinder and you run a bigger jet the colder the weather is. dont use to small of a jet in the summer or you will burn up the engine.