Thank you all for your advice and insights. Thought I'd share what I've learned so far from this post for the benefit of future readers considering the same issue.
I've never heard of "glass transition temperature" and didn't know what that was. So, with the issue of safety coming into question, thought I'd look deeper into the subject.
According to the mother ship (Van's), black on cabin top is not an issue structurally. Fiberglass top is made from same material and process as the cowl, which routinely sees very high temps from engine heat and does not suffer any loss of strength. The structure will not weaken due to the heat of dark paint. They pointed out that on Cirrus, it's an issue since the wing spars are carbon fiber. Carbon fiber IS affected by temp more than fiberglass. Support also said that the strength of cabin top would only be an issue if you flipped the plane over on it's top. It's not an issue in flight.
So, at this point it's the opinion of Van's that the issue is one of comfort only. (Which is still a major consideration.)
After stewing on this a few days, I am starting to lean away from "black" and am looking at more of a "charcoal gray". Might mitigate SOME of the heat (not all) while still giving me the high contrast look that is so appealing on the design.
Thank you all for your responses and insights!!! Very helpful!
N783V - Reserved
Flying Mooney M20J
Emp Kit Completed, Section 29 done, QB Wings delivered and stored for now.
Dues Happily Paid 2018