SD67, how about a 20mph wind layer at, lets say 17k. With the way the bomb-sight is calibrated presently, those 25K bombers couldn't hit the broad side of a barn. Making accurate bombing above 17K problematic at best, and keeping bombers within reach of the defending fields fighters, if they want to be laser accurate. Above 17K you would have to run mass bomber missions, and plaster the whole area to make sure you got targets down. Messy but effective, and historically accurate to boot.