From: Saskatchewan, Canada
Zuluhour raised this topic with me in an e-mail. I am replying in the forum because the research I did may be useful to others.
A review of several sources suggests that the daytime 10,000 ft limitation is unsound historically. In "Shattered Sword" Parshall & Tully state that at Midway the initial B-17 attack on the troop transports was flown at 8,000-12,000 ft (p106). The first B-17 attack on the carriers was conducted at 20,000 ft (p178), but the second was done at 3,600 ft because the planes didn't have enough fuel to climb higher (p329)!
At the Battle of Bismarck Sea in 1943, according to Bergerud in "Fire in the Sky", B-17s attacked the Japanese supply convoy from 6,000-8,000 ft. (p590). Bergerud also notes that the 43d Bomb Group used B-17s for low level night anti-shipping missions at 2,000 ft and under in 1943 (p589 & 593).
I found little on night attcks against airfields, other than a report by a B-17 crew member of a single plane night attack on Rabaul at 500 ft in Bergerud's book (p541)!
The foregoing probably warrants jettisoning the day time altitude restriction. As for night operations, given the apparent consensus of forum members that the game does not handicap these in a realistic fashion, I think the night rule should continue.