The white on-off oring on the classic valve is teflon. The white one on the retro valve is urethane. The teflon ones don't work properly on the retro on-off assemblies. You will need the proper one. The pin from an emag is 0.712" long. The pin from a standard retro valve is 0.750" long. Using a quad oring on an emag pin is the same as using a white urethane oring and a 0.725" pin.
You should get a proper X-vavle oring kit so that you have all the orings on hand in case of a failure. The quad orings don't come with the kits. You will need to order one or two separate from the kit.
Does your retro valve on-off cavity have the indentation for a single oring on-off top or is it flat for the two oring on-off top? If it is flat, make sure you use the two orings on top of the on-off assembly. If it has the indentation, only put the one oring in.
Except for the Automag in front, its usually the man behind the equipment that counts.