Well, it's just how things lined up. I've read about the boots, and I've got a discarded tire on the workbench at the moment. Now or never kind of deal. The seat bag isn't that crowded, so I thought I'll have a go at it.
And you know how it is. Now that I've thought about it I'd jinx myself bad if I didn't do anything about it. So it's either make a boot, or suffer a bad sidewall tear first thing next ride.