It is important to note that when using AES42 one mic uses one AES42/AES connection so on a 788T you would only be able to use 4 Digital mics.
This is only true for the Neumann and Schoeps AES42 mics.
The new Sennheiser MZD 8000, AES42 module for the MKH 8000 series, is 2-channel. So you can connect two heads via a Y-cable into the MZD 8000 and use just one AES42 input - so this would double the number of mics you can use.
I am just about to do this with my NAGRA VI - but I will have to use the Neumann AES connection kit to do it - powered from the Nagra and fed to the AES3 input.
I *do* hope Nagra will be able to enable AES42 on the NAGRA VI at some time.