Thanks very much for the comments guys!
I have also been posting my progress on 'The Replica Prop Forum', there a member called Bloop mentioned the oddness of the four rectangular boxes at the rear of the ship where the landing gear are, in the CG rendering they are solid boxes, but the McQuarrie paintings they seem to be four huge doors or flaps.
Bloop's comment caused others to dig out other reference material.....material also drawn by Joe Johnston, making me question who came up with this design? McQ or Johnston?
A larger image front on:
Approaching the Death Star:
Joe Johnston's sketch of the underside, you can see four hinged flaps:
The front view, he has noted the doors:
The Cockpit:
Joe's sketch of the Death Star Approach:
On to my progress:
Should be making the cockpit soon
Thanks for looking
John