I have a Saito 100 in my 60 size UCD. It is fine. I like it a lot. I think you would have a hard time with balance with a 120 in there. And I don't think the power would be necessary. Mine weighs 7 lbs 8 ozs. (after repair from my last stupid) The 100 flys it great. I don't really want more power in it. gjeffers had one with the 100 also. I think he liked it but now he's power hungry. He'd be able to give you an idea also. On the 60 thread most are liking the 100 but some have changed to YS 110 and say they like the plane better. I'm leaving the 100 in mine.
Thanks,
Barry