Hmm - decided to reduce the crew to 2 with the gun and the others on separate bases.
I've been doing a bit of research and found this excellent page on Nigel Evan's Royal Artillery website - which I've always treated as Gospel whem looking at British Artillery http://nigelef.tripod.com/anti-tank.htm It gives a pretty full explaination of who did what and where in the six man gun crew on a 6Pdr - well worth a read, but here for the impatient is the "back of a postcard" version.
No1 - Gun Commander - this is a Junior leader in Chain of Command so I need to keep him separate from the gun should he "cop one". His position would usually be a little away from the gun anyway - close enough to call targets but not too close as to get under the gunners feet.
No 2 is the loader. He would be positioned on the right of the gun breach close enough to load (dur)
No 3 is the Gun Layer - this is the guy who aims and fires the gun, His position is immediately to the left of the breach behind the shield where the sight is. I don't think there is a seat on the 6Pdr as most pics show him straddling the trail. I suspect it I had known this before assembling the model I could have got him in quite close to his real action position, as it is he looks ok
Nos 4&5 are around to help pass ammunition to No 2, and help move the trails if needed. This is pretty much the equivalent of "holding the coats" in a bar brawl, so they can be based separately.
Lastly No 6 would act as 4&5 or could be the "Link Number" who would relay the orders from No 1 to No 3 if for some reason No 1 needed some separation
Chain of Command allows an anti tank gun to function normally until down to 2 crew - although without the Junior Leader they will be disadvantaged. This makes me even more certain that I should reduce the crew on the gun base to 2 - No 2&3, and have the rest based individually. At least that way it will be easy to know when the gun is in trouble - when I run out of "spare" Numbers!