SX50 Handheld speed

I now that this subject has been aired before but I have just had an interesting thought (I dont have them very often!).

Despite the IS I like to apply the principle of not using a speed lower than the zoom length (e.g. 600mm and 1/600)

I have been using this as SLR equivalent length. Does this principle still hold true with a compact zoom and apply to SLR length (1200 at 50x) or should it be the true mm length of the lens (215 mm or thereabouts at 50x).      Bob