Thanks Wozza, but that didn't fix it :'( I moved the
prop_blurred part to the end of the list, and it made absolutely no difference. I even did a cut and paste to move one of the wings (the very first parts added) to the end of the list, so one would be before
prop_blurred and one after it, and it didn't change anything.

Here's another thing I noticed, it's probably related. I was very happy with my wheels, the spokes are just disks painted black with the alpha channel making everything except the spokes transparent. Take a look at this next screenshot.

The wheels are transparent between the spokes, but when you look through the wheels you can see that the spokes themselves (the non-transparent areas) also vanish and make the wings disappear! You can see the struts (which don't turn transparent) through them, and even the clouds on the other side! Again, moving things up and down the draw order makes no difference at all.
If anyone has FSDSv3 and wants to take a look at the .fsc file, just send me an email. I'm stumped!
Gryshnak