I tested random bases on SFMA, Crater and Euro2015.
At 50% fuel using auto takeoff the 29 failed to take off on all runways tested with exception of A1 on the crater map that sits higher than the surrounding land. As a side note. Earl, if I remember right, has always said said use no flaps on b29 takeoff. I was able to manual take off on some runways with no flaps.
In much earlier testing the b17 had problems above 50% fuel but I do not remember the earlier map that wee used. On the maps I tested today, with 75% fuel the B17 had no problems on the bases I tested.
It would be good to have other players post which map, airport and runway if they hit trees.