Um, the original question was about 'supercruise'? By that, I assume you mean supersonic cruise without the use of reheat thrust. I seem to remember being told by my Dad, who has some considerable experience on all marks of the Lightning from the P1B to the F2A, via the F1, F1A, F3, F6 and associated T-birds, that the early aircraft could maintain a low supersonic cruise without reheat, depending on altitude and temperature, but that the later, heavier aircraft could not. I will check with him to see if I've remembered it correctly!