Supercharger height for Il4 bombers?

[stugumby]

I am trying to figure the cruise settings for the Il4 series of bombers, in the 412 cockpit guide it has supercharger switch height of 4000m, but no rpm guide. currently using alt of 4200m at 75% power 65% pitch, gives 2000 rpm, mix 80%. speed of 270 kph unless carrying the big fab 500 bombs. Seems to work ok, just seems nose up trim is bad until tweaked. Anyone have any data or ideas to share?