If you're using a dichro head the usual rules of thumb for VC heads don't quite match. With my Durst M605 color head I find it necessary to make exposure adjustments with as little a change as from neutral or Grade 2 to either Grade 2.5-3 or 1-1.5.
This could be due to the condition of my filters or personal preferences (I tend to print dark) but in my experience with this enlarger and Ilford and Agfa variable contrast, multigrade, whatever, papers, the transition from neutral to either direction via magenta/yellow filters is not linear.
Being a lazy bum I haven't bothered implementing the various techniques published on the web to accomodate these differences. I simply make new test strips in quarter stops when changing a full grade or more and go from there.