We've charge extra for wraps with liquid lam too--but that is on vehicles. It's a PITA to work with because you have to tape it. Then you have to take the tape off. Trailers are a different story. Liquid lam'd cast vinyl is very conformable, and works perfectly around rivets.
I'm definitlely trying to talk the client into using standard lam. It all comes down to price though. They can pay the extra $$$ now, or when they remove the wraps. They understand this. Thanks though!