Im having some problems with thinking of what to make my wing harness out of and how to do it. The wings will be made of foam board and are pretty large in wing span, however they will be quite light weight.

It needs to go under a thin costume like a school outfit/shirt/blazer so i cant have it too bulky either.

Can anyone help me?

There's this wire stuff you can get from B&Q, can't remember the name of it but it's like a thick version of what they use for wire hangers.

Make it so that it makes a rectangular shape to go against your back and then it can follow the top/outside edge of your wings.

I've only ever worn wings made with copper tubing and that's roughly the shape it was but obviously with...copper tubing LMAO