My wife's mare currently has a 4 1/2" bit and it's just a bit too small so fine for light riding but not really fine.
5 " is too big so 4 3/4" would be just right.
Ordered a 4 3/4" curb from a website that also had them listed on e-bay...wrong bit showed up and now they are told the bit isn't made anymore (SUPER irritated with the company although they are handling things ok, but still got our hopes up)
Will a 5" shimmed down with bit guards work? In my mind I say yes but then the port wouldn't be proportional as compared to a 4 3/4 or 4 1/2 bit.
At my wits end trying to find one and every one being a dead end lead...hoping that my new horse (yipee) isn't quite the pain to shop for.