I was thinking the same thing. A hypodermic needle to inject the glue, enough so that the fabric is permeated about 1/4 thickness with glue. Too much glue and it bleeds through and looks bad. Too little and it won't stick. If too little is used and it has to be redone it would be horrible. It needs to be done right the first time. I have mine, and I can say that the fabric is a bit thick and tends to pull away from the body enough that the fabric would have to be held firmly to the body until it cures completely. I only hope the solvents in whatever glue is used doesn't compromise the bond between the paint and the polystone, if it's painted there.
Since the whole thing will be glued down, I think the hole from the needle should be able to be made inconspicuous.
Whatever glue you use, it needs enough time to be spread on her butt while it's still wet. I would want to avoid glue on the suit, because of the risk of bleed through. As such, I would not want to smear the glue on and even it out by pressing on the suit. I would only want the suit to make contact after the glue is spread, and then hold it against the body somewhat firmly.
