your wankels should be just fine in a royal dc-3, i went to school for mechanical engineering and design, and i plan to resurrect royal products.
there is a guy on rcuniverse who built a royal b-17 with 4 wankels, not sure if it ever got flying.
http://www.rcuniverse.com/forum/twin...al-b-17-a.html
http://www.rcuniverse.com/forum/twin...al-b-17-a.html
royal kit forum:
http://www.rcuniverse.com/forum/rc-s...oyal-kits.html