Shhhh! I was going to ask why Cedar Fair doesn't run two trains on Invertigo next!
Invertigo does fine with a single train.
I do think Wicked Twister could benefit from two trains, though. In fact, I think the improvement would be smashing.
They could have a quick transfer track so one train could load while other was going through the course. However with increased downtime likely from that they probaly just better off with the one train.