Some horses love a single joint bit, others hate them. See how he goes in it, if he doesn't like it you might want to try a double joint.
Having a bit that is too big is a problem, as it creates a different angle of contact on the mouth, I would suggest getting the correct size asap.
It is MUCH better than the bits you've been using on Clippy, I'm sure he will appreciate it.
PLEASE get his teeth checked when you can as well.