I have three semi-sizable (6, 8, and 14 gauge) piercings in each ear. Since I've started training with bogu (armor), figuring out what to wear in my piercings under my men (helmet) has been a challenge. Obviously I want something that won't potentially lead to bleeding when I'm struck! And I'd like to have jewelry that I can leave in during practice, so I don't have to fiddle with taking out jewelry before practice and putting it back in after and potentially losing it.
Fortunately I already have a couple pairs of Kaos Softwear Silicone Hider Plugs, which take care of my 6 and 8 gauge holes. They're soft and flexible and work great!
I'm having less luck with my 14 gauge piercings. I tried Body Bonz, but I really can't recommend them. Despite being advertised as flexible, they're really not. Two of them also managed to fall out of my ears in the span of three days (when I wasn't even training!) So until I can find something better I'm stuck with wearing my regular jewelry and taking it out for the duration of practice.
 i'll write more about training with bogu in a later post.