hi - mike 21/10 will work - i use a 21/10 on a zdz 40 - 21/10 props are hard to find - i use a22/10 on my da 50 and going to move up to a 23/8 - i would say just don't crank it out - da 50 is big time (OVER KILL) for that plane - you will lkie this plane -it flys great - good luck bill