vinyl sliding door problems

I have a vinyl slide door frame that istill bowing down from the top center causing the non movable glass to bend out. With the glass bent out it causes the door to be difficult to close. My question is how do you shim a vinyl door. is it the same process as a aluminum sliding doors and what about the outside frame, do I make some clearance between the stucco and the door so it would allow for proper adjustment of shims. Long story short how do I shim a vinyl sliding doors

vinyl sliding door problems