From what I recall 5mm spacers are too much for the studs, not giving enough thread for the bolts to secure on to. And ideally you'd want the front track increased by the same amount for handling characteristics.
I had 3mm spacers on the front to allow clearance when I fitted my Spoon monoblocks with OEM alloys, but then didn't need them once I bought the Advan's as the spoke design and offset gave much more room.