FX impact m3 fine tuning

not new to tuning pcp but new to tuning with the valve adjuster. i'm shooting 30 cal hybrid slugs in 600mm barrel.
wondering if there is consensus on fine tuning with hammer spring or valve? what i mean:
- i'm looking for 950-960 fps per fx rec on the hybrids
- start off with heavy hammer spring and valve wide open
- increase reg to get to around 1015 fps
- reduce hammer spring to around 965 fps (about 5% off plateau)
- increase valve till fps just starts to drop which puts me right around mid 950's

question 1 - if i want to start playing with velocity to get best accuracy (say go btw 930-970 in 10fps increments) should i adjust hammer spring or valve?
question 2 - once i find the best accuracy - lets say its low at around 930, i would probably redo the above steps to have lower reg pressure to bring the plateau down around 980-990 so i could tune 5% off plateau and be right at 930 - does that sound right?

thanks