Hi Rich,
Awww Man! I totally forgot to give your turret a try. I offered to help you "next door" a couple of weeks ago. I am such a bad person :cry:
But, I see not much has changed, there is only so many ways to skin a cat.
Have a look at the little Star Trek diorama I made (err sorry I have not uploaded that one here yet
http://www.kartonbau.de/forum/index.php?page=Thread&postID=457893#post457893) the caps, sorry BUSSARD COLLECTORS on the forward parts of all of the warp engine nacelles are half spheres made with just 3 pieces.
Why don't you download the model, and play around with those shapes...you could with a compass, vary the width of the strips adding more if needed to build the sphere you want. Then when its perfect, scan the parts and your ready to texture or whatever.
Not that I would presume to answer for Zathros, but Rhino differs from Gimp in that you design, develop and export 3D shapes. Other programs that you may wish to look at are Sketchup, Blender and (not a design tool exactly) Pepekura.
One of the things that are charming about your work that you have shown us so far is the simple yet convincing to the eye approach you have taken. I do not think you should stray to far from this formula.
Kind Regards,
Cris