Hi Chris, somewhere on the forum I have seen a thread where you place a small sand bag or one of those heat pack bean type bags under the area of the neck to worked on to support it when you gently tap down the high riding frets with a nylon faced hammer. They can be quite expensive hammers and I have used a rubber mallet instead and it did the trick. Mind you, the better way to go if using a rubber mallet is to use a bit of scrap maple, usually from a headstock shaping off-cut, place some grit paper face up over the top of offending fret and gently pass the timber across the fret to sand into it a groove to match the fret profile. Once done, remove the grit paper and place the groove over the fret and gently tap away on the flat 'top' side with the rubber mallet.