The Kwik Fli II was designed as a "smaller" version of the Mk.I, to be flown with the still popular Veco 45. As you may expect, with proportional radio "excessive power" became a nonsense, and quite soon Phil used a Veco 61 or a Supertigre ST 56/60. By the way, the aluminum plate mount can be used with the same hole pattern for both the Veco and ST engines. Webra Black Head and ST G-60 Blue Head (I like this one much better) can also be used, but they were released between 1969 and 1971, according to the different versions, while the Kwik Fli Mk. II was designed in 1965. I used an ST 56 on mine.
Happy flying!
Beppe