Instead of using the "voice stack" to phatten up a patch - duplicate the track on your host and detune it. I find that the CPU is much less likely to cry when you do this. I can only guess that a second instance of the plug can then be run on a separate thread/core where as using the "voice stack" it cannot. (Comments??)
Also good for getting extra polyphony on pads etc. With some tweaks on your host you can make a template which will route different midi to different plugs. I did this on Tyrell N6 to get 16 note pads. Sweet phat lushness...
Yes, there are some disadvantages - like tweaking the patch needs to be done twice but nothing a copy'n'paste doesn't fix.