That's the data from Pro-Ject directly. Effective arm mass: 6.0g
That's not including the weight of a cartridge or the mounting hardware (the Debut Carbon has no headshell, the cart mount directly to the arm). Everything said and done it'll probably be around 13-14g.
I think you've given me the answer I was looking for. I've been getting the feeling that this is a really nitpicky thing that I likely won't notice and even if it is noticeable it will likely be eclipsed by the gains from going to a quieter, overall better table anyways.
I think I should stop over thinking it and just throw the VM95ML and, barring absolutely terrible performance, just call it a day.