I dont think theres a right and wrong, but id say 99.9% of belly piercings are on women. And the only ones ive seen on men where gay men.

Im into tattoo's (i have 8 and there not small either) and have had in my time 3 bars in each eyebrow, ma "ahem" and my labret, only got ma labret now but i do fink its a bit for lads to have there belly done. Even ash who owns the tattoo and piercing studio agrees.