404Titan,
Would be interested in your quoting your reference.
Any suggestion that pilots ought routinely to determine the real world Vmca on the day is fraught with danger. There is no practical need to do so as there is no sensible reason for a civil aircraft to be close to or below the published certification Vmca.
For military operations, if the tactical need is there, the TPs probably will have done the work anyway and provided the data for operational application.
Mind you .... not always does the certification do all that is sensible ... often only the minimum requirements are addressed.
Although it is of little practical significance to the discussion, current FAR practice refers to Vmc rather than Vmca.