I have VW grey rubber front, rubber midmount, solid rear. I also have aluminium spacers to replace rubber blocks on midmount if necessary. this was suggested to me by Max Morley.
Surely that would create a stress point around the rear mounts, if the rest is rubber mounted it will try to move around the solid mounts?? I would have thought you would want all rubber or all soild?
to be honest i have no idea, but if max said it.....its probably okay.
I do know once you mid-mount the front mount is not needed, so the rubber here must be to stop vibrations and noise.