Ummm... Freak is always a good choice. Some don't like 'em...But meh.
Ultralights are also nice, and look pretty nice with the gun.
Stiffi's are light and accurate, but I'm not too keen on the look of them with the Shocker.
I'm currently using a Freak back with Teardrop front (14") and works nicely. But to be honest the All American is a very good barrel. Bore size is good and it's got a good accuracy. All personal preff. though.
Russ
Oh, BTW, Shockers don't need another barrel, they rock as they are