How did you stick the plasticard to the pens?
The 2 pens were fixed to the plastic girder with UHU, as the rough bond would be hidden by the next stage. I then stuck one end of the sheet to a pen with superglue then, once it had dried, wrapped the pre-curved card around and glued the overlapping plastic card (hidden on the underside) with EMA Plasweld.
I am impressed by your skills in finding and using scraps. A historical model makes it more difficult, imo, to be creative.
A completely fictitious model means no-one can tell you where you are making a mistake.

It also allows you to use any component you think fits in, rather than having to find something (or build something) that matches a component in a real item. I admire any build in this contest re-creating a documented (real or imagined) craft.