Fox T

You will need to glue those corner edges on the header seal, Make a template/former to the profile of the screen frame and the same width and apply a contact adhesive to both sides of rubber and roof frame. I glue mine from the bottom of the curve on the outward edge to approximately 4" along the top flat edge. When ready insert the said former and tape it in place and leave for at least 12 hours. when dry, remove the former and repeat to the other side.

If these edges are not secured they will roll in again and eventually deform to the point where you will need to replace the header seal completely. I have used an adhesive called super goop which seems to work well and any oozing at the edges can easily be rubbed off when dry without leaving a mark.