Those are good examples of where you might need to exercise some caution I would think?

Don't know about the 50's, but the 15cc engines are the same way. All they (HK) offer are the radial mount which are first generation. Way down on power compared to the V2 which is the beam mount. The RCG 30 vs. the more commonly available RCGF 32? Both have good reputations from what I've seen, but the 32 is probably a newer version? A reaction to the other manf's coming out with slightly bigger 30's (eg DLE 30 vs. DLE 35)?

If the latest and greatest isn't important, is down on your "must have" list, the engines may represent good value...... to some. That's my take anyway. -Al