The elusive Mystic 90 was discussed here (RCU) more than once. The '90' version, like most other '90' sized pattern ships of that era were really sized for a good 2-stroke 45. The 90 4-stroke referred to was any 4-S engine not built by YS. The original YS 91AC put out almost as much power as the original YS 120 and wayyyy more than any other 90 4-stroke available at the time (or since). It's a shame that none of Prettner's designs after the Magic were ever published as plans or kitted in an all wood format (MK). I guess EZ was the 'highest bidder' and wanted exclusivity. Then their factory burned down... I bet Don Carlson at RCAIIR could produce a nice glass/foam kit from an original EZ kit. Anybody have a Mystic 60 or 120 they could send him?