I have a couple of EMT-1's and EMT-10's. Yep, you need two of each for 16-note polyphony. Each unit is 8-note polyphonic but they have a great odd/even note mode that let two units work in tandem to provide 16-note polyphony.
Anyway, on to my topic. I can only find 1 pair of holders and mounting plates. If anyone has a set they can pass on or knows where I can get a set, please let me know.