20" 5.56 upper questions

[ut755ln]

I have a Noveske Gen 1 lower receiver and a VLTOR Noveske marked upper that I am going to build out. I want to do a 20" barrel and I have some questions as I have never built longer than 14.5".

1) Do I need to use a rifle length buffer or can I use a carbine length and adjust the weight and spring? Are there particular brands or systems that I should be looking at?
2) I am planning on shooting with a suppressor, on a rifle length system do I need to install an adjustable gas block? The barrel manufacturer says that the gas port is .089"
3) How long does the hand guard actually need to be? I am planning on installing a bipod (Atlas). Will shorter hand guards inhibit the functionality of the rifle?

 

[TonyTheTiger]

1) No, and yes
2) Not necessarily, depends on how picky you are about fine tuning things
3) Personal preference, there's a lot of reasons to go long, and not many to go short, but do what you like