There is another spring mod for the 510 that involves putting the spring horizontally.
This is what I use, and I like it. However, you have to take the foam out each time you fill it. But the 510 takes about 12 drops this way vs. 2 drops without the mod.
I would think with the vertical mod you also have to take everything out to fill it.
Not sure which is better !
(Sorry no reference, but it's on this blog.)