Howdy Nick,
I believe I presented my solution to you on an earlier thread of yours. It went something like this:
I gotta tell ya, I purchased one of the MTH TMCC/DCS cables and I was going to connect my LIONEL Base 1-L to the DCS so I could run my LionMaster Conrail SD80MAC equipped with the LEGACY Control System through the TIU using the DCS Remote exclusively. Well, I chose to connect the Base 1-L directly to my terminal block, (using 18 gauge wire from the "U" post on the Base 1-L to the negative side of the terminal block) and control the Legacy engine with the Cab 1-L instead of using the DCS Remote. I have been able to run both the Lionel Legacy and MTH Proto2 and Proto3 Engines simultaneously using the Cab 1-L for the Legacy engine and the DCS Remote for the MTH engines . They work GREAT together without any conflicts so far. I am using the "Star" wiring technique as described in Barry's book. If you don't already have the book, get it. It's worth its weight in gold. Just my 2 cents, your mileage may vary. 
Chief Bob (Retired)
