Not sure why you would want to use FBA. You already packaged the [posters and they are ready to ship. Using FBA will suck out all of your profit when selling FBM, all you need to do is print a shipping label and keep the profit for yourself.

Smart seller always test sell their products for a month or so using FBM. that way they know if there is enough profit in the product to pay all the fees Amazon will assess, and still have your desired profit remaining.

Think it over before it is too late.