If you want to use pens on clear nerf guns, use pilot g2 cartridges. They are more expensive, but they hold alot more ink, and getting the ink out is easier and quicker, just hold it over a lighter or soldering iron and the ink will all drip out. Then you could use a paintbrush or something to apply it.
I think it would be more useful with a draw-extended Nitefinder on the bottom,angled at 35 degrees without the linked triggers and stock because dtb's don't shoot very far or accurately, and the stock is just deadweight.