I owned an Slashs Signature amp. I sold it because I am idiot
I have now 3 Marshall Heads (6100 LE 30th Aniversary, JCM 900 SLX and 1959 HW modified)
The 1959 HW modification consits on having 2 Master Volume and 2 gain controls. I added one ECC83 extra tube and deep control for the Power amp section. I can use any volumen combined with any gain so I have 4 different possibilities.
Using different Kind of preamp tubes you can get the Slash exact sounds.
The settings for my amp are:
Presence: 7 Bass: 8 Middle: 6 Treble: 6 Master Volume 1: 3 Gain control 1: 7 Gain Control 2: 3
The gain control 2 adds the extra fourth tube on preamp section and gives extra gain. It is fantastic up to 5. Upper limits the sound becomes fuzzy.
I tried out the Setting's that you listed for the slash Marshall jcm2555sl... I like it.. This tone doesnt sound like guns days more like Snakepit .... Please let us know how old are these settings