Ok I'm not an engineer, but here's my 2 cents.... (Only applies if SFMM actually wants Twisted Colossus to duel)
Based on simple timing the 110 second mark might be the maximum time to allow trains to duel (i.e. Train 1 leaves, if train 2 hasn't been dispatched within 110 seconds, then Train 1 goes through the course the second time without dueling). Going through half of the course will take less than a minute, and based on the animation where the train rockets up the second lift hill, I can't imagine it would take 50 seconds to get to the top (Original Colossus took 30 seconds from the Bottom). The only way it would take this long (50 seconds) is if the 2nd lift slows down waiting for the 1st train, at the maximum time of a 110 second interval, but if the 2nd train is more than 110 seconds behind the 1st, then Train 1 will simply be sent through the 2nd half without dueling, so that Train 1 isn't waiting on the lift hill forever. This could mean that we could see closer to 90 second dispatches, which puts capacity around 1000 riders per hour.
Also given how slow RMC's (with the exception of Outlaw Run) make their way through the Break Run, I think this would only work with 4 trains.
I hope I made sense.