I only have this Amtrak HHP8 starter set (plus one K-Line dome-observation):
I have added the two-car add-on set plus the cab control car; at first, I thought that the short (18') would bother me but it really does not. The only problem for me will be two-railing them.
A couple of Amtrak photos that I have taken over a few years; Washington Terminal:
And here is AMTK 1 during a crew change somewhere in NC:
30th Street Philadelphia: