In a 10.4" setup with a VLTOR A5H4 buffer system unsuppressed, I experienced the following:
Welded gas block - Over gassed. Hard cycling. 100% functional.
0.035 gas port - Feels just right and cycles/locks on last round with low pressure ammo. 100% functionality.
0.050 gas port - Under gassed. Low pressure ammo won't lock the last round open reliably. I have not ran it hard this way, but I worry about cycling issues over an extended period of use.
I have Jason's gas block modification with gas port inserts, rather than a fixed port at 0.035. For suppressed, I believe the ideal middle ground is 0.035 (I believe that's what the HK vented 10.4" gas blocks are at). As mentioned before, the 0.035 gas port cycles my 10.4" upper on a VLTOR A5 buffer system unsuppressed. I am waiting on my paperwork for my suppressor so I can't speak to how it will run suppressed.
I would talk to Jason though. He's gotten feedback from many customers and personal testing as well. He's a good guy to chat with about these things and doesn't bullshit you.
Additional Note: I have ran the 0.050 port on my upper before with a PDW system and that cycles just fine with consistent lock open on last round, but this is with a PDW stock and buffer so it's not applicable if you have a carbine or rifle buffer.