Put it on like a built up wing.   Dope around the perimeter for a enough dope on the wood to get a sheen to it.  Light sanding to get wood smooth.   Lay Poly-span on surface and smooth it out as much as you can.   Then dope down the perimeter to attach.   Then the hot air gun to get rid of wrinkles and to tighten it.   Then start doping as you would a built up wing.  Remember Poly-span is a synthetic material that replaces silk-span.   

Make sure the shiny side is up.   

On a sheeted wing I use silkspan, easier to get it flat and smooth vs Polyspan, and you don't need the extra puncture resistance of the Poly. 
Thats the main advantage of Poly over Silkspan on open bays..

Carbon fiber is so expensive and in my experienceis no stronger than silkspan or Poly-span.   That is if you use dope to put it down.  Now with Epoxy it is a different story.