Help with selecting 9mm upper

[Quirk]

I have an  SBR lower and I'm looking for a reliable quality 9mm upper assembly. the JP GMR-13 upper attracted my attention.   Those folks at JP are very successful apparently, very busy, since I've gotten only terse cryptic email replies and no calls back after leaving messages a few times trying to answer some questions.   Doesn't discourage me, since everyone seems to gush about the JP quality.  It's just that their Rifle Builder feature on the website doesn't help me with SBR-specific questions. So I thought folks here might help answer some questions?

First, I hear that 9mm uppers can be temperamental, and I was wondering if folks had found the JP version to be more reliable.

I want to use a 10.5" barrel that JP offers.  What length hand guard would I need to size it properly with this barrel length? (I plan to use a can sometimes, but don't want to recess the can into the hand guard.)

That dual charging system looks cool...but not $500 cool, IMO.  Are there functional (not just stylistic) factors regarding this to consider?

I've never used thermal dissipator, is that of value or even possible on a 10.5" barrel?

Thanks!

Q

[SpaceMan]

Ill address one part of the question regarding the thermal dissipator- don't bother. I highly doubt you will be shooting the gun fast enough to notice any difference.