I fully agree with Kevin.
If You wish to use the double chamber muzzle brake, Your panzer will be mora a G than a "F2" (this nomenclature was changed during production) as double chamber muzzle brake was installed (not always) from September 1942.
So if You want to built an F2 (ore very early G) with the double chamber muzzle brake it sholud most probably be a field repair (barrel and muzzle or muzzle only) or a factory overhaul (complicating the features of the tank, as during factory overhauls some early features were changed to the last ordered).
You can choose (mainly) between: if the barrel lenght should be 43 or 48 calibers, if the rear engine hatches will have the "Tropen" slits for improved ventilation (present on most ausf. G produced from June 1942); if there will be any additional 30mm armour welded on hull and superstructure front; if the turrent front visors will be two or just one.
For an "F2 or early G" You most probably have dunkelgrau base paint, from 18 February 1943 the Order was to switch to Dunkelgelb base paint. But You also have the option of "Tropen" painted vehicle shipped to Ostfront, so with 2/3 braun RAL 8020 and 1/3 grau RAL 7027.
I quite never see photos of Panzer IV driven with the driver head out the hatch, but the hatch will be often left open (but depends, of course, from the climate too).
As Kevin wrote, SS grenadiers (fomr mid-war and in cold climates) were often characterized by the fur-lined and hooded parkas and (I'm sure regarding the Heer winter uniforms but not for SS practice) they were recovered in store at spring to reduce the wear. I don't think that greatcoats were taken away from the soldiers anytime.
So if You tank rider had the parka, he must be an SS soldier and the panzer (most probably) too; if instead he wears the greatcoat, he can be both SS or Heer.