Robin, it is only fair we swap tips. You have my Lego jig idea for chassis frames, I have your build the tracks first.
Looking good Rory. I hate say it though, once you start scratch building things, you can't resist doing it more in future. Be warned you are on the slippery slope
BTW, the turret seats were black leather, not canvas but your texture looks good for that.
If you want to be truly inspired look at this 222 buildhttp://www.sixtharmygroup.com/forums/showthread.php?t=18722
Something you might want to consider in future, German Jerry cans (and later Britich WD copies) had a noticeable seam where the halves were joined. Some manufacturers give you an etch piece to glue between the halves, but a thin piece of card trimmed to the shape works just as well.
..and the handle part has a piece cut out where it goes over the join
If you have ever held a 20L can, you would know this is not the way to get a drink out of one, a bath maybe, but not a drinkhttps://i.pinimg.com/236x/05/87/9a/05879ac3df0c08fbe8ea7ce8e23295bb--king-and-country-military-diorama.jpg
From Panzertracts 3.4 re the bolted down turret on the Befhelswagen:
"The Turm is bolted securely to the Bugpanzer (front superstructure).
A cylindrically formed Panzerschutz (armor protector)is on the front wall of the turret. A light metall casting Blendenabdeckung (mantle cover) is bolted over the Panzerschutz. The openings in the Panzerschutz on the right is for a M.G. Kugelblende 30 (ball mount) and the opening in the left for a Blendensehklappe (vision port)."
Also the extendable radio mast (Kurbelmast) was bolted to the floor and raised up through a hatch in the Turret top, so a rotating turret was useless when the mast was extended. The additional mast for the top of the Kurbelmast (called a schirmantenne) was in a vertical tube also bolted to the turret floor.
You will find some good interior pics in the Panzertracts book as well as nice pic of a H with the fully extended antenna array