You got the math figured right Rounderr77 ... Grains are grains, so it doesn't matter what the material make-up of the tip is when married to a correctly balanced Skagit head.
The grain distribution within the taper of a Skagit is designed to carry a defined window of grains <> Exceed it, and the line will not like it, go under it and it ain't too pretty either !!!
... The same basic rules apply for the rod's grain window (it is defined on your DC rod): Stay within the rod's engineered grain window and you'll be fine.
The rod does not have the ability to differentiate, nor have a preference for Scandi or Skagit heads ... It only demands that these shooting heads fall within the rods grain carrying capability, and be of a manageable length in relation to the rods length.
The rod's only 11'0" so keep things short in length, including not only the head, but tip, and Versa/Poly leader lengths as well.
Use the Skagit's for down and dirty and the Scandi's for fine and far.