Talk:ID:914/@comment-24366645-20141013192644

As a rule of thumb, getting units to drop is easier on the higher stamina levels (the only exception might be Athena from the Gungho collab). So if you want the Rainbow Upa you'll have a easier time getting them to drop in the 50 stamina quests.

Also some believe that there's an "average" amount of drops assigned to some quests, so you can try to aim only for 6 and ! while hunting for these. Take this info with a grain of salt though, it sounds more superstitious than anything.