I'm average and I've tried a magnum on before. I didn't use it for sex though, I just masturbated with one on (I was curious and I wanted to test it out). It didn't feel much different at all and just felt a tiny bit more relaxed. It was easier to roll it down to the end of my shaft (as opposed to leaving about an inch of base, which I know is normal but it feels more secure when it's rolled down lower). I'm not sure if it'd slip off during sex, though I honestly don't think it would. The consistancy of how it remained on my dick was just about the same as regular condoms. If I wore the XL, it probably would though. I do agree with the marketing thing but moreso with the regular mags and not really the XL. You definitely need to be at LEAST like 5 1/2" around to fill one out without slipping out of it, from the sounds of it.