Oberon, as you have only posted 147 times (at this point), I am going to let the phrase "stealing of bits" slide, or not. Darth Panda is one of our esteemed members and is proud when some of his creations get reworked. And here, we "borrow parts", "stealing" implies using parts without proper credit, and I, sir, am no thief.
Now, to real business, as to your "method" while it may look right and work for you, I however prefer my 75mm-105mm in 4 pixel depth, my 37mm-70mm in 3 pixel depth and so-on. In my opinion, 75mm & 76mm guns look far too tiny in 3 pixels.
I completely agree that the muzzle brake looks disproportionate, and have edited it to reflect that. And matched it to actual photos of both of the Sherman Firefly IC & VC tanks.
On a side note, I could swear someone did the Sherman M-50 & M-51...