Hi,
A modeler's license comment:
The correct wheel size should be 20" diameter. The link and pin coupler should be centered on the end sill. To be compatible with HOn3 standards, the top of the draft gear box would be ABOVE the floor. Using 26" wheels and below the sill draft gear gets the HOn3 standards.
This product was to have been also usable for HOn30. By using N scale 36" diameter wheels and Mini Trains couplers, the HOn30 standards (also N scale standards) are met.
So these differences dealing with the couplers and wheels are not the issue. (hint).
Doug vV