This is an LA 40, not a powerfull BB type. A 10-6 is just about right on the money for that plane (an 11-7 is wildly too big to permit the engine to develop anything close to full power).

If you need more vertical, an APC 11-4 works well with the LA 40, but it will cut top speed.

If you want a bit more top speed, either a 9-7 or 10-7 will work reasonably well, but both will cut acceleration & climb (the 9-7 will give abit more speed & the 10-7 a little more climb).

Best choice --- 10-6.