Art,
A couple of things jump out at me in your last photo that I'll point out, which are admittedly nit-picky at this stage, but I'll mention them anyway.
The backsides of the armor plate on the gun have some ejector pin holes that might benefit from some filling, and the way the white is sprayed in there doesn't seem to be consistent with the rest of the weathering. My guess is the crew probably would not have bothered to whitewash back there, but if they had it should be showing essentially the same level of wear as the front. Lastly, the gunners and loaders seats were stamped steel rather than upholstered so they should be the same color as the rest of the gun mount (with a lot of wear from harness buckles, etc.)
Still a great looking project overall!