What are the effects of a sudden reduction of gravity ?

[Darth Tedious]

We've been into space, so in theory we should know the difference between a man's testicular blood pressure in microgravity and and his testicular blood pressure on the Earth.

In theory yes, but the article also mentioned a dire lack of research in 'sensitive' areas. That said, I think that the methodology you describe would probably work, as long as a the stress levels the mice experienced in the sling and in space were comparable. What the space program needs is more astronauts who aren't shy about their balls...