That`s up to you but 8mm sounds a bit much, I think most go with 4-6mm and some even smaller on lower bicep, I like to leave some for a "thicker armor"-look...but as I said, it`s up to ones liking On my next kit (in my hands soooon) I will make the bicep edges smaller to try and keep the bicep itself as small as possible, not too fond of the some what bulky look I have on this kit...well...whatya gonna do if you got bulging biceps right?!