Hey Guys,
After posting, and reading Red's response, in the thread about Kegels, which strayed into a little bit of talk about "reverse kegels", I think that there may be something to it that is applicable to this situation. Besides, all of the longer explanations of a "reverse kegel", Red stated casually that it is similar to taking a crap. (I was puzzled about the muscles actually used for the "reverse kegel" because there are no muscles in the pelvic floor which work in the opposite direction of the PC for example.) So anyway, whether it is simply a contraction of the lower abs or whatever, forcefully taking a crap, (or forcefully peeing), could pass as a reverse kegel.
Sorry, I ramble. What I am getting at is what I found playing around with this idea. While playing around with "edging", I thought it would be a great time to try some of these reverse kegels to see if it helped stave off ejaculation significantly without the need to stop stimulating myself. Well, it worked like a charm! Whenever I got near to the point of ejaculation, I simulated, or contracted those muscles which you would if trying to force out a big turd, and the feeling of impending ejaculation would pass, even though I did not decrease or stop stimulating my penis at all.
What it felt like to me was this. It seemed that the contraction of the abdominals or whatever somehow forced downward towards my pelvic floor, with most of the stress directed toward my anus or sphincter mucsle(?), BUT>>> There felt like a distinct decrease in blood or the pressure of blood in my penis while doing this contraction. It had the effect of eliminating or significantly reducing the sensitivity in my erect penis, and virtually eliminating any urge to ejaculate. And it felt like my overall hardness dropped the very instant that I tried to "take a crap".
Just thought that I'd share what I experienced with my experiment with "reverse kegels" and how it might help you with the question you posed in the OP.