Thank you all, gentlemen!
So far, it's been a relatively easy build but I have this strange feeling I failed to add sufficient nose weight. We'll see how that pans out.
The extra glazing came from the Airfix kit, which supplies two cockpit glazing options (the differences are forward of what I used). If I did it again, I'd cut along a few of the frame lines at the front of the glazing & wedge them apart slightly with some styrene, so they match where they join the other glazing sections. It's hard to see, just holding them up, but the main cockpit glazing narrows towards the front by about 1-1.5mm, which becomes obvious once glued into place.
I'll use the same method with the next (cockpit forward) version I build (if Hasegawa are nice enough to supply two canopies for their B-25J) but just PSR over them to get the right contours. The cockpit forward version will, also, allow for more nose weight, which I believe is a problem for most B-25 kits.
Once more: Thanks for watching & commenting! Very much appreciated!