What's up with the orthotic shoe-like floor plates on the 45F? It appears that they had to make the mag tube longer than they originally intended. No chance for nice, flush floorplates on that tube. Check out the pic of the backstrap--the bottom of the mag tube protudes below the bottom of the grip, then they attach the huge floor plate to further increase the pistol's dimensions.
The HK45C likely uses off the shelf USPC mags, as the full size mag is actually a stretched USPC mag.
Something like this would be much cleaner looking, but they'd have to shorten the mag tube.