Nice job. For future reference a common way to do this is to line the trim you want to mark/place/identify with lipstick or another material that will transfer. Align your panel and then push it back up against the marked piece and it will leave an outline for you where it contacts.
I tried putting masking tape on the window then using a red Sharpie but the ink wouldn't transfer or transfer in sections on the back of my panel, maybe with lipstick it would've worked better, thanks for the idea!
DIY conversion build, extended 2010 Ford 5.4L E250 + high top, from Montreal Canada, new to all this so please be patient and clear with me (never built or camped in a van yet)