Question re 6-wheeled trucks/bogies

[RobertInOntario]

Walthers, "Athearn coupler" conversion kit, PN 933-997, $5.98, is the same coupler assembly used on the Walthers auto racks. I used them on my kitbash auto racks, that started with the Athearn 89' flats (with the long arm coupler mount). I couldn't run my racks with the Walthers ones, without derailments. Once my racks got the conversion kits, I no longer had that problem.
My CNW/Metra coaches, kitbashed from Rivarossi smooth side coaches, still have a dreailment problem, and that's with 4 wheel trucks. I suspect that the "offset bolster" actually causes the wheels on the "long end" to try to move farther than those on the "short end". Same with the six wheel trucks. I would expect better performance if the bolster was directly above the middle axle.

Thanks, as well, for this info. I'll also ask about the Athearn coupler conversion kit at my LHS as well. Cheers, Rob