Setting up Athete Power Zones

[JRZ]

Hello - I'm a regular TrainerRoad users and looking to take advantage of GC for further analysis. I've been searching around and experimenting & still don't feel clear on whether this is a necessary step or not. 

If there is no data all my zones disappear on the CP chart. Plugging in just 1 entry gets my zones to appear; plugging in additional entries does not seem to have any effect (perhaps it's subtly adjusting the zones on the CP charts)

My hesitance is that a majority of my efforts are in TrainerRoad 8 minute tests and I'm unable to isolate W-prime, PMax and CP from those short efforts (and particularly PMax requires a separate test as i understand it). Is GC working off the body of work and does not require me to extrapolate the testing data? Or am i short-changing myself on valuable info?

Any advice is greatly appreciated.

Thanks,

-John