Leave it alone for now if you're gunna stretch it. No matter what you come up with you'll have to do it all over again with the stretch, anyway.
The Banshee's a fairly decent shock but once you get a stiff enough spring on it it tends to overpower the rebound adjustment.
I got it to work fairly well with an XT600 spring, but like I said that all goes out the window with a stretch.
The Blaster shock will give you a nosebleed. Lifts the rear on the order of 5".