You might want to add that one major reason to go with a Bp/wing, is to gain a stable platform that holds the tank to the diver's back, as if it was part of the diver--with no flopping around. If you were to use a fabric "backplate", sort of an oxymoron, you would now have an unstable foundation for the tank to be attached to...the diver could move one way, and then feel the tank moving around on his back, hopefully to regain it's position soon...this flopping around is undesirable, and why a fabric "backplate" should be considered a defective choice. You could probably make the harness out of paper also, but that does not mean you "should"...