Thanks Ken, Dave and Alexis, I think the assymetry is from an unequal twist in the blades. From most angles it looks OK, well certainly good enough for me!
Today I have been putting the undercarriage on which involves attaching a few rigging lines that will be inaccessible later. I forgot how fiddly this stage is and am not very much looking forward to the main job. Hope to have pics of the legs and wheels in place later tonight.
Richie