While I keep the same pitool at 2, base SteamVR SS 20%, per App SS 250% (assetto corsa), no advanced supersampling filter, which makes a total SteamSS of 50% and a total SS of 50x400=200%,
this leads to a resolution that is not the same everyday.
One day it was 4828x3216, the other day it’s 4828x3116, and today it gives me 4828 x 2980.
In clear, the first number stays the same, but the second number keep changing and I have no idea why since I don’t change anything in the game.
I made a test with FPSVR to detect the resolution in game, and it gives the same resolutions I just stated.
Edit: mystery solved
it turns out it comes from the different screen vertical offset value I used in pitool that changes the vertical resolution.
with vertical offset at 0 Left / -0.5 Right I get 4828 x 2980
with vertical offset at -5.5 Left / -6 Right I get 4828 x 3344
with vertical offset at +5.5 Left / -6 Right I get 4828 x 3496
putting both vertical offset to the minimum -10 or maximum +10 gives me a vertical resolution of 3608
with both at zero vertical offset it gives me 2980
So, using the vertical offset in pitool only to raise or lower the virtual screen can lead up to a 21% maximum increase of vertical resolution. good to know in term of performances impact !