I did this with a G2 of mine several months ago. I found that while it is an improvement, the improvement is pretty minor. G2 rollerballs are very good pens to begin with. My suggestion would be to perform this 'hack' once the original refill that came with the pen has already run dry. That being said, I also wouldn't consider the improvement it made for me to be worth the very high price of Mont Blanc rollerball carts. If anybody still really wants to give this a go, I have a new MB refill that somebody can have.
medium black ???
I will take it...