I have two of the DDF40Xs. Took some time, but I have accumulated brass fans, grabs (18" & 15"), plus side railings for doors, and hardest to locate, screen material. In all, extra parts were costly, but worth it for a nice representation. I used a micrometer to measure Bachmann window inserts, and interior width. I decided to use Micro Kristal Klear. You can also use this "white glue" material for lamp lenses. I did add a thin plastic strip to sides, as length allowed a very slight body flex. Other than that, both are perfect. What I was wondering, will there be a "B" unit available for the DDF40X ?? My units will be painted for 60s-70s Alaska Railroad.