OK, that's appreciated - but don't get too carried away.
At some point I can potentially see the 2 machines becoming one, and running LS under windows directly alongside cubase.
(I'm waiting for an upgrade for the 24-channel interface to arrive so that I can run it on a quadcore, at which point my main DAW will become powerful enough to meet all my audio + sampler needs all at once, though I might keep them separate as 2 quadcores)
(Also, I tested the VSTi in cubase earlier and found a problem - I reported it in the windows beta thread).
EDIT:
Answer to Q1)
I think I tried all combinations of using some audio ins + out and no audio ins + outs with reversing the master/slave roles.
I mostly found that transmission of both MIDI and audio was unreliable.