ORIGINAL: JWN
The only complaint the owner had about the engine was that the idle was fairly high 3K+ so landings were a bit tough with the engine running.
The secret to getting a good idle with the HP is to use the right plug and let them *really* warm up before you try to idle them back.
The one in my Cub is mounted inverted and won't idle very well when first started but after a minute's running at full throttle it will idle forever -- and so slow you can almost see the prop turning. In fact it idles better than any of my other 4-strokes.