@patrik:
It sounds strange, the monitors that take so much time to switch are very old?
I tried that when I had a CV64 like you and it worked without problems with an old c= 1942 and a Hyundai Deluxscan15G+.
Now I have a Picasso4 and I didn't have problems with a 17" Medion or my current 20" Eizo...
Mmm I think you should disable Screen dragging, it slows down switching and doesn't look as good as aga... for example drag down a 256 colour opus screen if you have a 16bit WB under it... colours will look crap. I have disabled screen dragging (well, now I use P96 and don't have that option anyway)