I have taken the plunge and have an iStar Anastigmatic Doublet 127mm F12 R30 objective on the way for my scope build. I had originally wanted to go with the 150MM but it was not available (yet) in R30. The focal length will be 1476mm. Spot diagram is here:
http://www.istar-optical.com/sd-127f12-as30.html
My scope design will be along the lines of the iStar TCR, an open strut and ring structure, in many ways similiar to the designs that Dennis Steele of Dobstuff uses for his scopes. This design will give me a very light scope for its size. My goal weight is to keep the total weight below 7kgs and this is very achievable, given the objective only weighs 3kg.
I will not be using any aluminium or steel in the strut structure, the rings will be made of marine plywood and the struts themselves of Tassie oak dowels or battens. It will be assembled on a jig to insure alignment and I will be using boat building epoxy systems to bond it all together into a monocoque structure.
I will resort to aluminium for the back plate, and of course the focuser will be a Moonlight of similiar.
More info, photos, and updates to follow once I get started on the build proper.