Need help with multiple Alesis ADAT XTs

[payday2323]

I have a recording rig that consists of two Alesis ADAT XTs. My goal was to have a mixer feeding two separate Presonus D8s (each is an 8 ch. Analog/Digital converter that sends out 8 tracks down a single ADAT cable), and then go from the D8s to my two ADAT XTs. This works fine but as soon as I connect my 9 pin sync cable between the ADAT XTs, the slave automatically goes into EXT external clock mode and it can only take ADAT input from the master XT.
This is very frustrating. My goal was to be able to record 16 tracks of audio at once and have the two machine be in sync so I can mix and control the two tapes like it's all on one machine, but it seems that syncing the two XTs and making one the master and one the slave is only good for sub mixing tracks from one machine to the other.

Does anyone have any thoughts or solutions to this problem??
Is there an external clock override on the slave XT?
Is there some other clocking or sync unit I need for the two machines?

Any help would be very much appreciated.