I think mine is a Mk1-which I've had since the mid 80's. Found it hard to start-but in hindsight and with a lot more experience of large diesels since I think the PAW recommended prop sizes are a little too small. I concur absolutely with the benefits of a big heavy glass filled prop-the lighter wood or nylon ones don't have the flywheel effect and these big ones seems to benefit from plenty of flywheel effect. 13x6 even 14x6 they take in their stride. Eventually you have to decide between bhp and higher revs versus the increased efficiency and much better handling of a large prop turning at lower revs. My GB5 and Sparey 5cc both very happy on 13" and 14" fans-but these are big sideports with Mills like handling so can hardly be compared with a front rotary PAW-all mine are standard versions so I can't comment on throttling ability