Other than deleting and re-creating, I have not found any way to do that.  Of course, once the part has been used somewhere, that option disappears.  We have a few cases of this happening so I will watch with interest if anyone has a solution

Correct.

once a part has inventory it is locked in its serial characteristics. even if you delete all inventory of that product it still remains in the logistics transaction log and therefore remains locked. 

I was afraid that was the issue but was interested if somebody had a workaround.