You might also want to ask this question in the Sheet Metal forum.
I have this vague memory that in the bad old days, one way to set up certain properties in your templates was to make a part with the proper properties, then delete the part before saving the template. The properties, or at least some of them, would be saved even though the part was gone. I have no idea if this trick would work for your issues, nor do I know whether this trick still works at all. For that matter, maybe it is a bogus memory and it never worked.