Not about mast bumping but Re: side wards flight.
R22.. fast side slip or sidewards flight, it may not be written but maybe the words of the sentence that are missing may be to do with the doors, think of the door on the low pressure side during a slip and the vent opened on the other, and door is only pinned with a single pin!, i have seen a door double up and seen a few with stress cracks, may be something to concider.