[MENTION=42101]masi61[/MENTION] - never having mounted a tubeless tire on a bike, I'm definitely not the person to ask. I would think that sealant would prevent you from tossing the tire, but I have zero experience to back up that WAG.

I think I have some 16 and 19mm kapton tape - having used it I prefer it to velox cloth tape. I would be tempted to try a small piece, maybe a foot long, and see if that works. One problem is that the tape's adhesive needs to hold in the presence of sealant and I don't know whether the two are compatible. That's why I suggested a couple of wraps. If you start past the crack and wrap towards it, after one layer you'll actually have two at the crack. Continuing on, this time past the crack, you'll wind up with three.

Since not all rims are built like yours, some rim tape must work with sealant or rims with spokes holes could never be sealed reliably. Hopefully someone with experience can chime in.

But maybe, Shimano will just replace the rim and this discussion will be moot.