transporting a sliding glass door without a pickup

I don't want to pay to rent a pickup and it's a bad idea in general to lay large pieces of glass flat in a trailer or across the rails of a trailer bouncing down the highway for 2 hours. So I was thinking about using the step rail of this Yukon to build out a shelf on which I could perch the upright sliding glass door. The door is 6 ft wide by 6 ft 8 in tall. I can put a piece of 4x8 1-in foam between the door and the truck or maybe not because it's a new door and it will be packed in its box. I'm attaching photos of what the support under the step rail looks like. The side rail is all plastic except for the metal supports of which there are four along the length of the rail.

Any ideas about how I could attach to this metal that's holding the step rail? Maybe I should detach the step rail from it and then I would have more room to screw a piece of wood to it?

No picture...

Trying photos again

Would it not fit on the roof? well tied down including a strap running to the front tow point?

The roof rack is only rated for 100 lb I think and the window is 150. And again, flat a great way to break the glass.Plus then I have to get it down from there by myself. Another good way to break it.

I think Skandi might be on to something. I would buy or borrow a full sized air mattress. Inflate it 3/4s. That way the rack would hold some of the weight and the roof would hold the rest of it. I've used air mattresses this way many times to move glass in my pickup. You will still need help getting it up and down. So..... buy some beer and visit your neighbors. That works for me too.

An air mattress is an interesting idea. I don't know about you but the ones I buy never hold air for very long.

I have noticed they get transported standing on the edge, often against a leaning rack.
A 6x4 trailer with a rack built with timber bolted with lock nuts may be good value to you.

Actually, I slept on air mattresses for about 12 years after I broke my back. They helped a lot. Some held up for a few months and some for a few years. I still inflate one and lay it in the bed of my truck whenever I transport something fragile. Lay the glass on top, tie it in place and it has a comfy ride home.
But Denise could take the plastic off the railing and see if mounting wood to it would work. Still, a 2 hour trip on a highway would be a tough journey. I would take side roads all the way and drive slowly if it was me. If it fell off and broke a cop would give her a pretty hefty ticket to pay!
But I decided my last suggestion could be the best.... buy some beer and get to know your neighbors!  Possibly one that has a pickup truck!