Re: DRGW 73 dual gauge draft gear

Hypothesis:-The dual couplers may have been a bear to operate with, they are really close and may have caused issues with coupling and operation on curves, but I presume the only curves in their scene of operation would be the diverging road of switches.
Observation:-On 73 at least, the adjustable coupler appears on the cab end, the dual couplers appear on the hood end in all the photos I have seen (stand to be corrected), maybe it had both all the time for what ever reason, testing each one maybe but the testing never finished or came to a conclusion so why bother???
Question:-Now that this subject has been raised, I have wondered at times whether the common rail is always on the same side, photo evidence tends to back this up and now that I have seen other diesels with this dual coupler arrangement I think this may have been so, all the narrow gauge couplers are on the same side, if the common rail changed sides at any location they would not have been able to coupler the SG switcher to NG cars.
Further question N strictly NG, what model switcher was 73?