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I went through a long excersize of what is needed to activate Nulti Segment metering when I looked at converting a K mount to KA mount.
In the end it is really quite simple. Note all pin references are relitive to pin 1 being the closest to the lens locking pin
For multi segment metering to work, you need to have pin 3 shorted to the mount AND pin 7.
Pin 3 is the tricky bit because it is recessed so it cannot come in contact with any metal lens base that is on the camera, pin 7 is the data pin, for AF lenses.
Pin 7 is a raised pin, and must be shorted or you will not have the camera accept that there is a lens on the camera.
Pin 3, is the A position pin. As I said above, it is recessed, or perhaps flush to the camera body. It does not matter because on K mount lenses there is a slight recess, perhaps 0.2-0.25mm deep over the data pins, so that this, along with a recessed pin 3 ensures that no K mount can be interpreted as KA because they just can't short the A pin on the body. BUT, it might be possible for an M42 mount, which is flat, and not recessed, to contact the A pin on the mount if the pin is just flush with the edge of the mount.
This is something that can be easily checked with a flanged adaptor. Does the flanged adaptor appear as an A series lens??? On my bodies no, but if there was any moisture or some conducting contamination on pin 3 and you have shorted pin 7 with tape, it could happen
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