You are right on the 'above sea level' thingy, and I'm okay with 205* on the TT. I have check the Guru which is right on.
I have spread 4 probes around the pit and have not found excessive variation....maybe 15* to 20* which I expected and reasonable.
A longer TT probe would make a difference in the right direction, BUT..... something sucking the temp down on the TT which the Guru confirms.
Note; I never checked the Lang.
I was thinking of wrapping the TT threads with Teflon tape to see if it has an affect.
Anyone using the TT in their pit as the temp guide may want to check grate temps. When I cook to the Guru my TT is around 175*