I'm looking to build a 9mm upper and currently have an Vltor A5 system with their A5H2 buffer (5.33oz) on my RR.  I am looking to purchase a buffer with my goal being a smooth, safe SMG.

The heaviest buffers I've seen are the Vltor A5H4 (6.83oz) and the XH (10oz) from Heavy Buffers. While having a sufficiently heavy buffer seems to be the primary concern I've also read that limiting bolt over-travel to protect the bolt catch is recommended.  It looks like most people are adding spacers if they use carbine length buffers/extensions or they buy purpose-built buffers like the 9mm-Q (which appear to be A5 length).

So my questions are:

1.  What weight should I get?
2.  Should I be concerned about bolt over-travel and, if so, how should I address it?

Also, what barrel profile (weight) is appropriate for a FA 9mm upper?

To add a little more info...

Clint from heavybuffers.com recommended the A5 XH (10oz), a Wolf XP Rifle spring and a spacer (or a custom built A5 XH that is a bit longer).

Thoughts?

I'm looking to do the same, did you ever get anywhere with this?