Haha by all means do whatever you want for a story. I have no problem with ridiculous sizes if they’re where they belong: in the fantasy section.I read a bunch of posts on that thread. I'm considering downsizing this giant character's dick a little bit, down to 9.5" x 7.5" now. Partly because I think it's be funny if even genetically modified giant super human would still fall slightly short of that number.
I could envision him thinking he could win a contest like that, measuring wrong, with a soft tape around the curve of the head. Then measuring his girth too close to the base and having the thickest portion of the spongy part his urethra included at well. He'd think he's gonna make an easy 10k with an 11"x9" monster, only to find when it is properly measured with a ruler and around the mid shaft, he falls short of 10" in length, and isn't even quite 8" around either.
I don't design characters specifically to pick on them, but often it's when someone falls just short of something and seeing how they handle it that is more interesting.