I have a Nubra, though I've never danced in it. I got it mostly because i'm a 'barely B-cup' hippie girl that hates bras & has no modesty, but sometimes pasties just won't cut it or show through. I really like the Nubra, though when I've worn it on hot days, it can feel kinda gross when you get sweaty. I don't think it slipped or anything, but you might wanna try dancing in it & getting sweaty in it before a performance just to make sure. It will also bounce along with your natural boobs, which might be distracting while you dance. Last, for triangle tops, the place where the Nubra clips might show. You would need a triangle top that is sewn up a bit in the center. i hope that made sense...

other options, i know many gals who wear bras under their cholis for more oomph, and you can even use convertible straps if your choli is backless. harder to find a bra for under a triangle top, though.

Decorations! They're gonna be your best bet... When I make a bra, I have to go easy on the decorations & keep them from covering the entire cup of the bra, or my girls look insanely large (more than normal) -- so it would make sense that going full-out with decorations on yours would have the opposite effect - more chest!

Wear a decorated bra *over* your cholis. You can also sew padding/cups into your triangle bras to help -- then decorate, decorate, decorate! And think 3-D with your decorations to visually "build-up" your chest -- like turkomen buttons & larger upholstery tassels.

Also, my smaller-chested troupemate wears 2 bras when she performs, to make her look like she's got more than she actually does. One regular one underneath, that fits her well, and then the decorated one on top. Just a thought.

you can also get built-in bra cups (like the kind they use for swimsuits) that you can sew or pin directly to the inside of your costume top.

Oooh...oooh...push up pads with lil velcro pieces on the bottom that hold them in place...that's what I use when I wear triangle tops and such...we're probably about the same size and it actually gives me a lil bit of cleavage...woohoo!!!

Nubra's and similar products (sticky boobs etc.) work very well to help women like use have more shape.
the only problem is, if you're in a production that requires a lot of sweating...the adhesive starts to fade and the bra can start peeling away from your chest. if you have time inbetween numbers to stick some doublestick fashion tape or glue back onto it, that'll work.
but sometimes I feel very uncomfortable knowing my bra is coming off while I'm dancing.