That much track on one TIU output will very likely create DCS operational issues. You're talking 350 feet on two levels, far more than the single TIU channel is designed to drive. I predict that wouldn't end well and you'll be back here trying to solve that problem.
If you want to insure you don't run into voltage differences, how about using a Z4000 transformer with the remote receiver. You can control the voltage for the Z4000 using the Z4K tracks feature of the DCS remote. That gives you remote control of the voltage and insures you don't have voltage differences on the different levels. Using that scheme, you can use the two fixed channels, one for each level. You'll have much better DCS functionality and you'll solve you voltage differential concerns.
