Are you talking 1.20 2c or 4c? As far as 2c is concerned, use a .90. Most .90's are in .60 size cases and the less weight the better. For a 4c, then yes the 1.20 is the way to go. I have 2 Ultimates, I HAD an ASP 1.20 2c in one for a short time. It was heavy and not worth the extra weight. Most guys are flying them with ST .90's and OS .91's. Another good choice is the Webra .91 P-5. The RCS 1.40 for gas might be an option. I tried a Maloney 1.00 gasser for kicks, flew it 1 time (yes it actually flew!) and that was enough.