It sounds like the engine is a little rich, but it's better to err on the side of too much fuel than too little. In particular, the P12 can handle a fairly lean LSN setting because there isn't much pinch between the piston and sleeve so there isn't much heat buildup from friction. Also, you can dial-up the shift point on your transmission significantly from where it is now; the P12 revs very easily and you're not saving the engine from any unnecessary stress by keeping the shift point low. I'm currently using an O'Donnell medium glowplug in my P12, but I've experimented with a hot glowplug in the past; as expected it idles more reliably and accelerates without bogging-down if it has been idling for a minute or two beforehand, but the hot glowplug burned-out after a few runs, whereas I've been running medium glowplugs in several engines for years without needing to replace any of them. The P12 is my only engine in the past several years that has actually burned-out a glowplug, so I guess I won't be going back to a hot glowplug in that engine. The P12 doesn't tolerate old glowplugs like my Taiwanese-made engines do, though; best to use only new or lightly-used glowplugs in the P12. Oh, and the shim stack can be lowered by 0.1mm (to 0.4-0.45mm) to get more torque with no ill effects.

That's all the advice I have at this point; I'm still getting my P12 tuned just-right.