No it's not the stock setting ! The stiock was 10 O'clock

I set the trimmer at 8 / 9 o'clock but it still a bit agressive (the picture was made with a different setting that I didn't like, to know if I turn my trimmer in the right side ^^)

Yes, look at from the other side, as simple as that.

maybe this helps

I have to agree.  I have been tweaking mine for a couple of weeks now, and have found that 8:30-9:00 position, or easier yet, just above being "off" on the internal trim pot, is really where the o.d. channel shines.  There is still plenty of gain to be had if you want it, but this "barely on" setting gives you the smoothest o.d., and more variations in tone from all the gain stages.    I can't stress enough how much the preamp tubes make a difference in a high quality amp like this.   This is truly an "audiophile" quality build, and subtle changes in the circuit will be heard if you have good ears and really pay attention to what kind of response you get from variations of just the tubes.  It's worth it, and you will find your tone if you take your time.