Will fashion tape fix this?

For my Halloween costume, I need to wear a strapless dress. So hence I bought a strapless bra. I'm 100% sure it's the right size for me, but there's one problem. My boobs are quite a bit fuller on the bottom then on the top. So this strapless bra fits very nicely on the bottom, but on the top not so much. This just causes my boobs to look kind of odd, and it causes me to feel uncomfortable due to the fact it feels as if the I'm kind of sliding out of the bra. Could fashion tape fix this? I'm going to wear this bra no matter what so please no answers suggesting I ditch the bra.