That's a good technique. I used the FR MEST around my sleeping bag when OhSki and I did the cold weather camp last winter. I did it to protect my bag from the fire's embers. I wish I would have tied the tabs together like you showed It would have kept everything together better for sure.
That FR MEST is one of my favorite pieces of kit. Dang versatile. I dig the new UL MESTs too but as often as I have it close to fire I don't want to give up the flame retardant on the FR version.