The most common description of "Tint" is based on a Green/Magenta Shift, built upon the Gel concept of Full Minus Green (-1) to Full Plus Green (+1). This is a more familiar concept to programmers/gaffers than ΔUV, though I assume that parameter would be useful in certain applications. Yes, the correct physical Units for CCT would be °Kelvin. Regarding Custom Parameters, it is important to also add the "wildcard" (n) option. Using the simple C1, C2, etc., has caused confusion since the "C" often refers to a Color Wheel. To leave that assumption in place, I would propose adding a "P" (Parameter) with a wildcard option...CP1, CP2, etc. This concept may also be useful for custom parameters in other Activation Groups B(eam)P1, BP2, etc. With the ability of Mode Mastering, a DMX channel may sometimes control CCT, and in other instances, it may control Red, or Hue, or some uncommon attribute. I would also add the wildcard option to other standard parameters, where there may be more than one channel controlling, say CCT on another emitter instance of the fixture or perhaps a base White Point underneath a color parameter. The same goes for Tint, or perhaps may be useful for multi-instance fixtures, such as the Mac Aura, instead of having the Aura be a ".1" fixture. I would suggest the structure CCT, CCT2, CCT3, etc. for additional instances of common attributes. Thanks!