I haven't, then again, I've no idea how to either, lol.
This is definitely one ruling I'd like to see, because my friend is running two or three CoA's right now in his deck which contains a buttload of flip effect monsters and a few "flip-summon" monsters even. It may not come up with him anytime soon, as he's unlikely to activate it during the damage step, but it would definitely be something nice to know. I was looking over the FAQ last night at UDE, and even though Blast with Chain itself has no rulings posted, a search on the A-C page resulted with this little tidbit under "8 Claws Scorpion":
[font=Arial, Helvetica, sans-serif] The ATK of "8-Claws Scorpion" becomes 2400 during damage calculation. You cannot chain "Rush Recklessly" or "Blast with Chain" to this effect. If these cards were activated before damage calculation, then the ATK of "8-Claws Scorpion" becomes 2400 during damage calculation so those cards have no effect on its ATK.
So just by that little thing alone would easily seal to me that Blast with Chain definitely can be activated during damage step. Now if we can only clear up the blasted wording on Curse of Anubis. It wasn't mentioned under rulings for any other card but itself, so that search was no help even.
[/font]