I didn't even know if it was practically possible. So, of course, I decided to try.
Now, I did this repair 31 days ago, taking photos and writing out my thoughts as I did it. I've resisted posting any of it until now because this was all useless information until some sort of durability could be demonstrated across daily use. Well, after one month of constant (and sometimes downright harsh) use, I've decided I can at least apply the label of "preliminary results."
What follows is what I recorded a month ago:
I wore this holster basically every day for 18 months until this crack got to be a bit too much for me to keep going.
I could have returned the holster under lifetime warranty for repair (a replaced Kydex shell, I assume) or replacement, because FoxX holsters is a really great company. But rather than cut into their bottom line just because they stand behind their awesome products, I purchased a second holster for the same weapon, this time from another company I'd also come to respect (RB Holsters).
Now it's a year later and I'm noticing that second holster developing a crack at the same point. Time to either send this in for a replacement... or find out if I can repair it myself.
I like the sound of the latter.