take me out and shoot me:
Ya won't take the DH with H-H motor, and now you want to trim down a fiberglass?
You have great luck in finding dishes.
Make room for one of those beauties at home! -
The edge of a dish adds stiffness to it. The fiberglass one has a wide rim.
Cutting that off would probably compromise its stiffness.
That said, the gurus with decades of fiberglass experience, comment that many of the really old one already sag somewhat.
As to technical discussion, the focal length would stay the same, but the F/D would change drastically.
You'd need to move the scalar closer to the dish, without moving the feedhorn.
Or in a worst case, you might want to replace the flat scalar with a conical unit.
And please..... find someone with the good sense to haul that DH & H-H home.
I want to see a happy ending to
that story!