Just A Thought; Any Inner Structure You Add Should Not Be Bonded To Flat Surfaces Where It Will Show With Temperture Changes Or Future Curing (try To Stick To Corners, Door Edges, Firewall, Etc). And I "would" Set It Out Outside On The Hottest Days Or Get It Into An Oven (enamel Shop), On The Frame As True As Possible. You Want It To Move Now Not After Paint.
Check Out A Wescott Catalog, They Show Their Inner Structure, Might Give You Some Ideas. Good Luck.