There is a video on youtube of a low level, cross continental, Hustler mission, so it was capable of low level penetration. Its handling was as I understand it not that different to that of the F-111 so fit a TFR and it could have been viable although I don't know how it would have gone fatigue wise. The issue was I believe its operating costs verses other types capable of the sort of missions it may have been able to move to. Now if anyone was going to take them low level regularly it would have been the RAF, I wounder of Hustlers would have killed off the TSR2 before it got seriously underway?