Bob, I agree with your assessment about the Kadee G vs. the #1 coupler.
Just to clarify for folks, the Kadee 906 kit (and older kits 830/930-rust color) and 907 kit (and older kit 789) both include “G” scale type centerset couplers. The knuckle portion of the respective coupler types are physically the same. However, the newer types emulate the prototype AAR “E” knuckle and are slightly lager. Corresponding Kadee #1 scale couplers are very much smaller.
The 906/830/930 has a long shank with one centering spring housed in a relatively large box.
The 907/789 employs two small side-by-side centering springs all housed in a smaller box.
The knuckle portion of respective types are physically the same.
Example Kadee 907:
Example Kadee 906:
Example older Kadee 930 - rust color (otherwise same as standard black 830):
The various 3-D printed CamPac boxes typically utilize the coupler, springs, and lid from the Kadee 907 or 789 kit - but obviously not Kadee’s box.
The smaller foot print of the box portion utilized in the 3-D printed offering is desirable for confined areas where space is limited, such as on locos, and where wheels may otherwise rub against a larger box, such as the case with USA Trains modern tank car when operated on tight curves.
CamPac offerings integrate the small box with direct body mounting adaption for selected products, including locos and cars. Coupler track height alignment is also achieved with respect to the Kadee 980 or older 880 gauge.
-Ted
