If the loops are independent you shouldn't have a problem as it is, but without a bit more description, I can't say for sure.
Jeff But it's a dry heat!
I'm not sure what you mean by independant. They are on opposite sides of the layou and each one has it's own reversing controller. The entire mainline is fed from one source, though.. if that makes a difference. I'm just thinking that if a loco were to hit each loop at the same time and they were at different polarities, they would creat a short when they both tried to switch the mainline to match directions at the same time..
I'll add a bit about why it works...
In DCC the "polarity" on the track doesn't matter tot he train, so you can switch the "polarity" under it, and it just keeps doing whatever it is doing. In DC switching the main to match the loop while the train was in the loop makes sense, in DCC there's no need to think that way.
Thanks, that helps a lot.. I'm a little fried today from soldering feeders to N Scale track all day and I'm not thinking as fast as I usually do..