Hi!
I started building my Marutaka DC-3 (Royal was the importer in the US) in 1980. Got it ready two years ago.
Mine is powered by two OS FS .26 four strokes, swinging 3-blade, 10x5" carbon fiber props.
Weight is 3,6kg ready to fly .
The DC-3 flies just as well as a high winged trainer,nice and slow. I have lots of wash-out built in the wing tips (1,5-2 degrees).
It takes of at just over half throttle so it got power to spare.

Do not power yours with too big engines if you want a good flying characteristics and keep the weight down.
I would recommend .30 four strokes engines max. Anything bigger would just make it into a pattern plane.
The engine recommendations on the plans is not right.They are a thing of the distance past...
C of G is correct on the plans though!