Ahhh. The Pandora's Box that is belt tension. I guess if you're using a Frequency Meter of some sort, then things are pretty definitive, if not just a little bit anal, especially on the 2 valvers. As regards the Allen key method, then I reckon your 5mm is my 3mm or perhaps my 8mm! The point being, the acceptable parameters are quite large. Don't fret (pardon the pun), just don't over tighten it, get out there and thrash it! After all, you're changing 'em every few hundred miles.
