Not sure how this will help as our is on a -10 however we have the Roll on 12 and pitch on 18-20 somewhere, I forget exactly.
I have found some interesting things with the static vents in the -10 of late and this plays havoc with the ALT and obviously the pitch! If the static varies a little bit you will hardly notice, but a 20 foot variation is really easy to achieve!
When I know more about the results of my getting the static sorted I might have more info, however we have the Aircraft Spruce vents, the flat disc type, and I found we had positive pressure in the static lines. Have glued a rivet head over the top and have been filing the edges to get the static right......a painful process. I am testing by doing TAS V Groundspeed box tests and hence I can tell what the Static is doing. Also comparing the GPS Altitude which I know is not rock solid reliable here but the trend is what I am looking for.
Anyway, you should give that a go.
Another trick I found with the A/P is that to stop the hunting trim your a/c so the servo has to work a little bit against the trim, it will come up with an UP or DN message, I keep it just flagging DN, only just.... seems to work well. Maybe I will not have to once i get the static sorted.
DB