The original question is a bit academic, as it's not the "largest penis only support group.org".
Photos are poor quantitative evidence, due to the distortions inherent in wide-angle shots - the same effect which makes the subject's nose look too big in portraits taken with wide angle (short focal length) lenses is obviously at work in the self protraiture on display in The Gallery. All that's definitely proven is that none of us belong with those unfortunates in the ratearod.com "Hall of Shame".
And a stated numerical size, even if honestly reported (well, it's possible, isn't it?), I suspect often comes from someone waving a yardstick somewhere near and just picking a number.
After my sole misadventure with a condom, during which I found (after much aggravation at a very inconvenient time) that the only size available in those days couldn't conceivably be made to do the job, I was inspired to make a device which would give reliable and reproducable measurements of length in a functional (rather than decorative) setting. The idea was similar to those things with sliding stops they used to have in shoe stores. (Yeah, yeah, I know, "goddamn engineers".) However, as not everyone has such a device (and, I suppose, not everyone would want one), it's useless for comparison. All it does is allow me to state that my claimed dimensions are traceable to the National Bureau of Standards (now, after a bureaucratic name change, the National Institute of Standards and Time).
All of which leaves us none the wiser.