oggyb - I found that when rendering in larger chunks for less renders I started to get problems with perspective and getting the top and the bottom of the strips to line up properly as well as things near and far away. This effect was minimised by using the small strips.
I will do some more trials and see if I can find a more efficient way.
Thanks
King_Tiger_666 - Not the first time I have spent ages doing something only to be told there is a button in photoshop that could have done it for me. LOL.
Photoshop just does so much that you could spend a lifetime figuring out everything that it does. Anyhoo, once I finally get a method locked down, I will write an action so it does all the strip combining, laying out, fading and combining automatically.
And that oggyb is the reason why I don't really want to blend the layers with a brush, but would like to do it with an automatic method as I plan on making lots of these for use as environment spheres in other 3D apps.
Thanks for the input though.
Back to the virtual drawing board.