I got this from the U - Can - Do .60 manual:

NOTE: Flying on the OS 1.20FS caused more tail weight to
be needed, made it so the plane would not sit still on the
runway and made it difficult to maintain a hover. The
hovering was hindered by using such a low throttle setting
that the poor throttle resolution made it very difficult to stay
in one spot. I do not recommend a 120 4-stroke or larger
engine if performance aerobatics are desired.

According to the manual they tested 4 engines

O.S .91FS W/O Pump
W/O Muff. 21.3oz
W/Muff. 23.0oz

O.S .91FX
W/O Muff. 19.42oz
W/Muff. 24.3oz

O.S .61FX
W/O Muff. 19.4oz
W/Muff. 23.6oz

O.S FS1.20S W/O Pump
W/O Muff. 30.5
W/Muff. 31.17

OK Ive read on here that the plane does come out tail heavy. seems to me that if you used the 1.20 that you would not need to add as much weight if any in the tail to balance does this sound right or am I missing something.? I'm going to be using the SAITO FA1.20S on mine 28.8oz w/muff. shouldn't have to add much weight if any should just be able to move my radio gear around I'd rather do that than add dead weight to the nose or tail.