This works best for me as a second instance of GP. Mostly because my machine is old and I use Diva And Tyrell N6 a lot, which are resource hogs, even when you tweak the Diva settings for efficiency.
This gives the OS the option of assigning a different processor core for the synths avoiding crackles from buffer underrun.
In extreme cases I would run the second instance at 256 samples. GP is quite happy with one instance at 128 and another at 256.
Although GP can work with many different sample sizes, Jam Origin MIDI Guitar is best efficient at powers of 2 like 128 and 256.