Backless Strapless Bra Backless, Strapless Bra Help.?

Backless, strapless bra help.? - backless strapless bra

Hello.
I've got a performance tomorrow, I shall be a disguise.
The dress is too deep to keep in the back to a normal bra.
and is a halter.

I bought one of these strapless backless bras with little sticky side of the page for the members.
Is this during my stay in power?
even if I sweat?

btw. I'm just an A / B Cup.

I thought the duct tape to keep up with the bra.
Good idea or bad idea?

thank you so much!