I tried the Jett in-cowl muffler for my OS 1.60, but it didn't fit into the cowl of my last plane (H9 Cap 232), so I returned it an opted for the BCM Pitts. I am sure it will give more power than the BCM Pitts does.

With 2 elevator servos at the tail and rudder servo at the wing, my Staudacher balances just acceptably tail-heavy: 30% aft from LE at the center of lift (40% from wing root to wing tip). I am sure with the Katana it should be better than Staudacher because Katana has a slightly shorter tail moment and less fuselage structure after the CG.