I attached a coupler to the front of a General's pilot truck after figuring out with a body mount, the front overhang pulled cars right off the rails in curves, or if heavier, the cars dragged the drivers off. I imagine fast angle wheels wouldn't do as well; the flat tread and deep flanges of early and loco wheels do a great job keeping the pilot truck on the rails, though you'd likely think "not". I think it's that the center of gravity and attachment point is so low; nearly at pilot truck axle height.
I expect making a "home-bilt" Vanderbilt tender would be pretty easy for you too Charlie.. hint, hint, 
