I’ve done the G-Nib conversation with the Jinhao. The end results weren’t too bad but ended up being a complete mess about 10% of the time. The results are great though.

I have the Jinhao set recommended in this article. It writes nicely and feels great in my hand but it leaks if handled roughly and it dries out sitting on my desk. None of my TWISBI pens have those problems. They might leak into the cap a bit with rapid pressure changes like on a plane ride but otherwise they are much more solid.