I now have a Beseler 45S color head that seems to be working OK. I am using a Stopclock Pro / Vario that was just paired with it's sensor in my Aristo D2-HI cold light head, worked great in terms of timing consistency. Since I am moving that head onto my CB7 bellows assembly for a soon to be mural enlarger, I have a spare sensor and was thinking if it might work with interesting results if put into the 4x5 mixing chamber of the color head. It would seem by popular opinion that Ilford MG filters maintain exposure in the mid tone while according to Richard at RH designs, the Vario paired with a Zone VI VC head pegs the highlight for consistency, the method that Ralph Lembrecht says is more desirable when calibrating a Dichro Color Head for VC papers. So I am wondering what might the effect be in putting the sensor in a logical place in the mixing chamber, like above the small square hole one finds in the styrofoam when taking the chamber apart? I can always just try it but I figured if anyone knew right away reasons for or against it, that is always better than drilling needless holes in things..