Power rating -- looking for regulatory guidance

I have a glider commercial rating, and I'm adding on my power rating. The question is, just what requirements do I need to solo?

Yes, I know the relevant reg --

§61.31 Type rating requirements, additional training, and authorization requirements.

(d) Aircraft category, class, and type ratings: Limitations on operating an aircraft as the pilot in command. To serve as the pilot in command of an aircraft, a person must—...

(2) Have received training required by this part that is appropriate to the pilot certification level, aircraft category, class, and type rating (if a class or type rating is required) for the aircraft to be flown, and have received an endorsement for solo flight in that aircraft from an authorized instructor.

The question is, does "have received training" mean "have received all of the training?" That seems pretty stiff -- you have to do the instrument and night cross country first. Does it mean "have received any of the training?" That seems (for the FAA) pretty loose, especially compared to the rules for student pilots. Half an hour of take offs and landings and off you go. It seems to mean, whatever it takes to satisfy the instructor that you're competent for solo flight, which seems unusually sensible.

My question here, since many of you may have followed this path, does anybody know of a letter, FAQ, or other official statement from the FAA -- the type that might convince airplane operator chief instructors, presidents, insurance companies, and examiners -- on this issue?

Thanks

John Cochrane (BB)