So there is good, but it comes with the bad.
The good is that all six of my custom cars are done. They all track exceptionally well, even being pushed as one whole block through the yard ladders! ... kind of blew my mind they performed with talgos so well, as expected having to body mount the couplers. The bad is the Centerline cars can't handle more than 2 of my custom cars in tow without derailing. Have to do more experimenting, but looks like I will just pull the 2 Centerline cars (one wet followed by one dry) alone, then a second section train with the 6 cleaning cars not too far behind. I was thinking maybe the 6 cars were overkill, but the last car in the string still gets dirt on it's pad after just a few laps on the layout. Overall the track appears to be pretty clean, and the units don't stumble following behind the first pass of the cleaner train. After track, its typically the Trix wheel cleaner to all the power, but more testing needed before I change anything there.