I remember discussing the RD-1 with Bob when it was "new". My oldest, Aaron, and Robby got to be pretty fair Buddies, and Aaron built the RD-1 (with foam wings) to be his first Contest plane. He now has a built up wing RD-1 for Profile class and practice.
We used the Webra 28 which when mounted sideways didn't have the burp that caused Bob to eventually swap the 28 out for a 32 in the Tucker he published. Aaron ended up with all Bob's 28 parts, including the one that was used in the Tucker Special. The Webra 28 is a strong little engine!
The RD-1 wing vs. the Twister............. same, same for all intents and purposes.