Try shortening the front end up a bit to increase the non-grip area in the barrel. It looks as if you've got the cap threads pushed pretty far back. I like to have my cap threads start a little bit behind the junction of the grip and barrel, but I usually only push them back about 1/16". It looks like you have a long enough grip to be fairly comfortable, so I don't think you would need quite so much added length to the grip. These short pens are much trickier to nail the proportions on. Good work though!