I never took the gay rumors about Rod serious, too much Brit laddishness in him. The guy who values male kinship too much to spoil it with sex. Not ragingly homophobic as "The Killing of Georgie" showed, but just not sexually thrilled by men over prolonged periods of time.
That is not to say that he might not have had sex with men at one point, Bowie, Reed and Jagger all flirted with it while being mostly straight. But that "just testing!" approach doesn't make you gay in my book, my (romantic)definition of gay is wishing to share the rest of your life with another man.
On the other hand I have to bow (but not too deep!) to your expertise, Mark, it takes one to know one. All the gay guys I know tell me credibly that they need a bat of an eyelash when meeting someone to decide whether he's 1. gay, 2. "incurably straigt" (or even a "Zwangshete" or "obsessive-compulsive hetero") or 3. "has potential" (but doesn't know it yet). And they are always right too!
