More styrene has found its way into 622 with the addition of the cab roof. I formed this by heating some .015″ styrene in boiling water and fixing it to the outside of a can of Green Giant Niblets with rubber bands and some scraps of card. The Cricut made the carlines (the transverse members that give the roof its shape, not the old Scottish woman) for me, and I cemented them in place while holding the roof to the cab. Building the roof in place means its a friction fit, and you can actually hold the cab upside down and the roof stays on. Some .02x.02 square strip under the eaves helps to obscure any gap.
The cab roof made from heated and formed styrene. 
The cab roof is a friction fit.
I made the smoke deflector with a scrap from the roof itself, with the edges thinned so they don’t look too chunky. It has a couple of little blocks to help hold it up; hopefully they won’t be too noticeable. I agonized briefly over its shape, and then just cut a slightly bigger radius than the cab end; solvent took car of much of the fitting.
Pembroke:87 