Not sure why you would want to do that but the customer is always right.
If you have a mixer. send the output of the KOSMOS to one input, and feed the same input sent to the Kosmos to another input with the polarity flipped. You should be able to subtract the dry signal out by summing these two inputs together. maybe....
or not... I wouldn't ASSume that the harmonics are generated as a discrete signal, and easy to separate out.
I believe this is patented so you can research and read the patent to understand more (maybe)... I think the design engineer may still work at peavey. So he would surely know.