Flash noseband for parrot mouth?

Would this work? I have a horse with minor parrot mouth, so he opens his mouth alot while I ride, as well as his tongue hanging out a bit. Would a flash noseband help at all?

My horse is severly parrot mouthed too. What bit are you using?

Is there a reason behind the horse opening its mouth? A lot of people look to a flash to keep a horse's mouth shut, but that's avoiding the initial problem..
Have you had his teeth done recently? Chiropractor out? Do your saddle and bridle fit correctly?

I agree with getting his teeth checked. But no, normally they will manage to find a way to stick there tongue out the side even with a flash on.

The tongue thing is usually a personality thing.. gaping the mouth open is not.