I've made the LV (ex PRR) Hammerhead, cut off the top of the short hood just at the begining of the curve, added a taller piece from another shell. Still need to add some inset louveres, the dynamic grille and steam generator vents on the short hood (and rotate the headlight). Waiting for parts from the new RS11 (sill and handrails).
I'd do the same for the CNW 1688. The FM hood is TOO wide as is, the top curve might be right but wouldn't be after sectioning, the curve of the front of the FM nose shouldn't . The doors are not close.
After splicing the 2 RS short hoods, I'd file the rounded corners at a 45* angle, laminate some strip on the bevel and recontour to a tighter radius bend and roof curve. Might just as well sand off all the detail on the short hood, nothing is close to being in the right place. (Except the headlight, and it needs to be turned.)
The doors would best be made by... there is no good way. I've scraped and sanded the back of a panel to get the louvers off to use elsewere. PITA. Or you could splice the doors from the long hood, suitably shortened. PITA.
It looks like the CNW unit has the last phase carbody filter arrangement, the front railings like the RS11. What will be some more fun is shaving off all the louvers off the long hood. BTDT for CNJ's later phase units.
Bob in IDaho