I have the six motor set in Santa Fe. Note that K-line made A-B-A sets in both 4-motor and 6-motor versions. All units run off of a single TMCC board in the lead unit. I have pulled 11 K-line 21" aluminum passenger cars with this set. That was probably not a good idea, but somehow the TMCC board handled the load. To be safe, I should probably rewire the units in series/parallel as Royboy suggested.
Bob Glorioso