I mix things if I have a reason to. Dan said I was crazy to cross a double and a poly my first year but it worked.
Of course you have a better chance at a good poly % by crossing two good polys together but if a poly I like doesn't have the branching/bud count that I want I'll outcross to a non-poly. We just talked about this on the poly robin. Bobby and Pat C. disagreed with me so there are different views on that. I've also been outcrossing polys to patterns.
ps...someone isn't buying any more Jolly Poly so hopefully you'll get the next one.