Tom, wouldn't increased car rolling resistance constitute- -assuming a consist isn't inordinately long, thus compromising the pulling ability of your motive power- -a positive trade-off with respect to coupling action. To wit: Picking up one or several freestanding lightweight/"easy-rolling" cars often necessitates that the moving loco [with or without attached cars] close in on them at a non-prototyptical high speed to ensure proper coupler engagement.
