if its a 40 size I'd put a 60 size engine in it,if it's the 60 size I'd put a 90 size engine in it. Caps fly better alittle over powered. I had a Kanke 60 size Cap 232 w/a 60 size engine. Had to put a 90 size motor on it because it was too heavy and had to fly the 60 size engine at full throttle all the time and it still felt under powered. The OS 90 was just the right engine. flew it all day long at half throttle.
NEDYOB