Thanks for the advice and useful suggestions. I will thicken up the fins for the next time but will do for the time being.
At present the holder ID is identical with the turbo flange ID. See picture below. There are no breaks - red circle. As far as the air is concern, it cannot see the gap at the intersection. The chamfer on the OD is gone on the anodised version.
I will also round off the tapered fin to minimise any notch developing. It is knife sharp at the moment.
