jetpack,
Using two needles is a primative form of throttle. You used one needle for high speed and two (or the other) for low speed.
Some would have one needle set lean and one set rich and switch between needles. Others used one needle for high speed and added the other (using both) for low speed.
I would imagine the two needle setup is as scarce as the cage mount for the Thermal Hopper. I have a couple of TH's but neither the cage mount nor the twin needle.
You should be able to run it fine with one needle.
George