Quote - So is it possible via ERC to slave a morph in two master dials?

You can slave a channel to as many other channels as you want. A separate block of slaving code is needed for each different master channel that you are slaving to, eg:

        rotateX xrot
            {
            name GetStringRes(1028,9)
            initValue 0
            hidden 0
            forceLimits 0
            min -100000
            max 100000
            trackingScale 1
            keys
                {
                static  0
                k  0  0
                }
            interpStyleLocked 0

            valueOpDeltaAdd
                Figure 1
                Bodypart_A:1
                Master_1
            deltaAddDelta 1.000000

            valueOpDeltaAdd
                Figure 1
                Bodypart_A:1
                Master_2
            deltaAddDelta 1.000000

            valueOpDeltaAdd
                Figure 1
                Bodypart_B:1
                Master_3
            deltaAddDelta 1.000000
            }

This is not meant to be a complete solution to what you want to do. I'm just pointing out that you can slave to as many master channels as you want.

You only give a very partial specification, so it's hard to know what you are trying to achieve, but using the new operator 'valueOpKey', may be more appropriate than 'valueOpDeltaAdd', providing it does not need to work in versions earlier than P7.