No! The main needle is not doing all the metering at part throttle. It has some influence but it is not the primary control.

Both of you have to realize that both needles influence the part throttle mixture.

The question is which one you adjust to get an appropriate part throttle mixture? If you peak the engine and back it off 300RPM you can't adjust the mid range with the main needle and expect the WOT mixture to be the same as it was, obviously. If the part throttle mixture is bad after you have set the main needle at WOT, you use the idle mixture screw to make adjustments to the part throttle mixture. Plain and simple. Dar questioning of the wording in that document is correct in that an inexperienced user doesn't realize that you would not use the main needle to correct a bad part throttle mixture.

If the carb is designed properly, (thankfully methanol burns at a pretty wide range of fuel air ratios) the part throttle mixture and idle mixture will provide acceptable operation.

Our carbs are very simple, comparable to turn of the century automotive technology. It works as long as you understand how to tune it properly. The fuel is tolerant of a wide range of mixtures ratios, so engines run just fine even if metering is less than ideal.