OK, TWR and Jeff agree with no support at 100. I'll leave it. 12x24 is a BIG target.
Its big, but under time, you have to learn HOW to shoot things like this.
Its not unlike bullseye offhand though, as long as its going to fall a 10, you generally don't care, and try to break the shot clean right then. As SOON as you know its coming.
If I could have ever figured out leading into a target I would have been unstoppable IMHO in offhand... I never could get it down reliably enough.
Should be fun!