After more than one week of struggling with the new setup I threw in the towel and went back to a Midi and audio connection of my slave Mac.
The setup never worked more than a few hours. Today, no matter what I tried out (Buffer size, thread count, even different Logic versions), Logic locked up when playing more than 4 notes (!) on the remote Mac. (Mac System 10.6.1 on both computers. One 8 core, one 4 core, gigabit Ethernet over a switch)
Other times it was crackles and drop out city. They went away if I changed the buffer size. From 2 to one to zero and back - didn´t mattter. it worked for a few minutes, then broke down again. (Note: It was downright impossible when BOINC or Compressor was running anywhere on my network)
Having VEP on my main Mac with System 10.6.1 basically - mostly - works. And is a huge bonus. But opening a connection to the slave Mac makes the master Mac very crashy.
Sorry to say this. Huge potential. Hope it works soon. Happy to give more info.
All the best,
Jochen