You've put a lot of work into that William and it's nicely finished and will work but if you had done a search first on here you would have found some good examples in the old threads.
I think Terry made a nice one and is the one mine is based on. Just a sled with angle and an old drill chuck to use your transfer punches so the exact fit for any pen tube. Much more precise and quicker than clamping to a mitre fence which has the potential to move out of true.
EDIT: I type too slowly - Peter beat me to it. Mine cost me nothing btw!
