That is the first reference I have ever seen of an Arrow 20 (and I have quite a few issues of Japanese model magazines). I don’t know why MK never kitted a 20 sized version, I bet it would have been popular. I scratch built 2 Arrow 60s about 40 years ago (I did use the MK fiberglass top deck which Indy R/C sold separately); about 8 pounds each ready to fly less fuel with a painted fuselage and Monokote horizontal surfaces. OS 61VF powered, they flew great. 2 years later I built an MK Arrow 40 for fun. Built almost entirely with CA, Monokoted and powered with an OS 40 VF it was a rocket. I flew it for more than 20 years. I sold the 60 sized Arrows and bought 2 Joker kits for turn around pattern. I loved my Jokers, but wish I had kept the Arrows!