Those look great. How did you secure them to the wall?

On the two large windows at the front we do not have cupboards above them. So I used a 1.5" x 0.5" clear pine wood at the top and bottom. I drilled through the pine and used #8 sheet metal screws to fasten them to the top and bottom of the window. The PVC sides are fastened to the pine with screws. I then used a piece of oak floor baseboard turned upside-down at the top to give it a finished look. We then stained it to match the rest of the wood.

For the rear window I did the same as the sides, but I used a wider pine board which I traced and cut to match the window trim contours. I then did the same as the front sides.

Where there are cupboards above, I cut the length of the PVC sides to slide up to the point where the wall and cupboard was the width of the PVC sides. I then used some "L" brackets made from scrap PVC and glued them to the PVC sides PVC pipe solvent/adhesive. I then fastened the PVC with a screw through the back of the cupboard into the PVC L brackets. The bottom of the PVC sides rest on the kitchen countertop or the blanket cabinet under the rear passenger window and the wood trim at the bottom of the rear driver's side window. I cut small "L" brackets and glued the L brackets in place at the inside bottom of the PVC sides and fastened through the L bracket with a screw.

Hope that helps.. clear as mud.

After heating and taking a "set" in the form, they have held the curve so far. I did this project mid April 2020 and they had kept their curve so far.