Multi channel recording using MR816csx and MR816x (MAC)

I have recently invested in the following recording equipment.: MR816CSX, MR816X, Cubase 6 and an iMAC running OSX Lion.

My intention is to simultaneously record up to 16 tracks using all the above mentioned equipment.
I have experimented with a Laptop running Windows 7 32 bit and managed to set everything up. However I could only record for about 5 minutes before loosing all input signals.

Since then I have tried to set things up using my iMAC.
My problem here is that although both the MR816CSX and the MR816X are linked together using a Firewire cable and also linked to my iMAC, I am unable to see both pieces of hardware within VST connections in Cubase. If I only choose one MR it works fine, but I need to record more than 8 tracks simultaneously

I hope someone can help