I started my first period since getting my small MeLuna last night. I'm getting some minor cramps with insertion and when I go to the bathroom, but other than that it's been perfectly comfortable and the capacity seems like it's doing fine. I was especially worried about this because I had been on antibiotics which screw with BC, and I think that's why my last period was relatively heavy. My first few days are the heaviest, so if I'm fine today I should be fine in general.
I just wanted to share my experience so far and thank all you ladies for all the advice and insights, I'd probably have panicked once or twice without it.
Oh, and I'm getting myself some cloth liners. My boyfriend and I don't do laundry very often (and need to go to the laundromat) so I was hesitant, but I figured that if I'm just using them for back-up it should be fine. I've been trying to change some things in my life for the better, and part of that is making my period a little happier :)