Exterior trim details for round window and metal siding – GreenBuildingAdvisor

Hi all, I’m installing a “outie” round Upvc window (flush with exterior insulation), then 1/2” furring strips and vertical metal panel siding.  My original trim detail is unfortunately no longer possible and I’m looking for some guidance on a new plan!

The original plan was to first install a custom round pvc casing, matching the depth of furring…1/2” (this is already fabricated and on site).  Overtop of this would be a custom round metal j-channel (with a 1” reveal of pvc casing) that would accept the cut metal panel. Alas, my local sheet metal manufacturer cannot accommodate the profile I need on his 3d machine.

What are some other options (ideally still using the pvc casing on site)?

1.  Could a round j-channel be fabricated by hand instead? It seems complicated to end up with a front “leg” with a paintable finish.

2.  Perhaps copper? But I’d have to separate it from the steel panel into avoid galvanic corrosion (would tape work?)

3.  Glued-up wood casing with a 3/4” jamb (to cover the panel edge/ribs)?

Thanks for any ideas!

Adam