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I really hate when my rear is stagnant. I'm just sayin'. In all seriousness though, I would guess he means staggered. Why you would want to go 20's front and back is a little bit confusing, since that will certainly mess up the personality of the car...but if you know that and don't mind, that's different I guess.
As for whether it CAN be done safely and all that, I have no clue.