After checking the aspect-ration of several prototype-photos against my model it became clear that the model's front-grill is no wide enough. After a month of consideration I finally made up my mind and have started to modify he grill.
I cut through the grill vertically, removed the outer half & enlarged the opening in order to shift the outer half of the grill app. 1 1/4" apart. Finally brass stripes of appropriate shape & length has to be fit to close the missing grill work.
upper picture shows current design, lower picture is a digital mock-up of new design