I've only had one air layer fail--and it was on a pencil-thin, green branch from which I tried removing a ring of bark. I must have scored the underlying, soft wood, and the branch cracked. I can't see what you'd have to lose by letting it get a bit thicker.
Since it's a sucker, you might want to wait a month or so and then carefully remove enough soil to see whether it's already rooting on its own. If so, you may not need to air layer it at all--just carefully snip it loose, making sure you've got some good roots attached.