David - I have two independent ovals just like you and agree with what's already been said. In my case sometimes I'll run TMCC or Legacy engines on the outer oval and conventional on the inner, or vice-versa; with just one CAB-1L. IMO the key (for me anyway) before I begin running anything is to ensure that the PowerMasters are set to the correct mode (ie. conventional or command) for the type of engine you intend to run on that track. Otherwise there could be disastrous consequences if/when a conventional engine gets 18 volts and goes flying off your track.
In summing up, when running 1 conventional and 1 command engine I merely toggle back and forth between each track using one remote. For the former I press TRack (1 or 2) then merely turn the red knob to alter the speed of the conventional engine, and for the command equipped loco I hit ENG (followed by the appropriate ID number and adjust the speed of the engine accordingly again by turning the red knob.
Good Luck and have fun with your trains!
That's exactly what I was hoping I could do. Thanks for the verification!