I would expect that the 11X6 prop you're currently running is close to ideal for aerobatic flying on the Tiger 2. It's not a 3D plane with large control surfaces, so the "larger column of air" benefit gained from a longer, lower pitched prop (like the 12x4W you were considering) wouldn't really help it at all.

A faster top speed will actually help the Tiger 2 with knife edge flight and some other aerobatic manuevers, so you might experiment with an 11x7 or 10x8 prop and see which you like the best.

If you're trying to step up to more challenging aerobatics and you feel like the Tiger 2 isn't capable of what you're attempting, it might be time to consider a pattern plane design like the Great Planes Venus 40 ARF or the Phoenix SeaBee or Laser. A "fun fly" sport/3D model like the Seagull Harrier .46 or Hangar 9 Twist could be a good fit for you as well.

The Tiger 2 is a wonderful airframe, but it does have limits to its aerobatic capabilities.