I learned (practiced) how to do this a couple years ago after reading a very hot self-suck story (that I can't seem to find anymore). It took quite a bit of practice and determination, but I could eventually get the head in my mouth with my legs up over my head.
I didn't do it for a long time, and gained some weight in the meantime, but I've started trying again every so often now. I can still get part of the head in my mouth, it usually just takes much longer stretching and working on the perfect position to get it accomplished.
My back usually tenses all up when I'm about to cum, which makes it hard to keep my cock in my mouth for the finish. I've cum in my mouth a couple times, but only swallowed it twice. I tend to have pretty big loads and I didn't find that part very enjoyable. I usually just pull out and shoot all over my chest/neck area.
I keep telling myself that I'm going to try to lose some of these extra pounds so I can go back to doing it like I used to (or better), but that never seems to happen lol.
BTW, I told then showed my current girlfriend and she thought it was pretty fucking talented and a little hot too. She even helped me one time by pressing down on my ass a little bit while my legs were over my head. Nowadays she's more worried that I'll hurt my back or something doing it than anything else.
Also, I've tried taking pics, but it's very hard to get anything that looks attractive when you're all contorted around like that. I'm not as skinny as LDH.