Unfortunately, the idea to use the bomb fins as the basis for the cruciform attenuator didn't work, the plastic became too fragile when filed to size to hold sufficient detail, so then I tried this..
I cut a cross-shaped notch in the end of an old artist's paintbrush handle, similar to how you would make a 'dum dum' bullet, and then inserted four pieces of very small litho plate, and then did a lot of very careful filing, almost blinding myself in the process, but, the results are pretty good so far, here you can see my attempt fixed to the etched brass screw:
You can also see how tiny the cruciform bit at the tip of the propeller boss had to be in order to be the right scale!
Chock