That's a great engine (my buddy has one on a Funtana 90) but my first CAP232 120 wouldn't even 3D with a Saito 180. It was much heavier than today's planes but still. You'd probably want more like an OS 160 for a 120 plane. Like take the Extreme Flight 74" Yak. It's light enough for a 160 but not the 120AX.

Maybe the Aeroworks Yak .90-1.20 Yak:

http://www.aero-works.net/store/detail.aspx?ID=288

72" wingspan. It might work with the 120AX. 9-10 pounds.

Servos, use metal gear. Anything 100 ounces or higher. The more the better for 3D.

Use a 6 volt pack. A123 is good. If you wnat to stay with NiMh, 2000 Elite or 1950 FAUP 5-cell/6volt. Use a HD switch. Cermark/JR is a good one.

This is a brand I'm not familiar with but a little smaller and lighter:
http://www.valleyviewrc.com/25%25%20...20Yak%2054.htm