Found the info for the B-17, it's in the airplane operations manual.
The angle for glide or climb is dependent upon which bomb is being dropped AND from which bomb bay station it is dropped from. Some limits are very low -- just 2 or 3 degrees while others are as high as 50 degrees. There is a note that states "Angles shown allow 10 degrees for safety. However, under perfectly smooth flying conditions, if in the airplane commander's opinion conditions warrant it, these give angles may be exceeded by not more than 5 degrees.
I will try and scan the page and post an image of it in the morning.