Does your bridle have slots on the crown piece (between the ears) for an overcheck to fit through? Some bridles don't have them so I would check that out before you order an over check. Just thought I would mention this to maybe save you some aggravation. I ordered one once and found out after the fact that it didn't work with the bridle I had so I had to get a new bridle. And the bit you are using needs to have room on the ring for the overcheck to attatch. Bits like liverpools and butterfly bits don't have the room because of the way the rings are made that the cheek pieces hook on to. You should have no problem if you use a snaffle or mullen mouth snaffle. As far as adjusting the overcheck, I keep mine loose. Looser than you would see in the showring. I have it adjusted just tight enough so they can't get their nose to the grass. It's a good idea to keep it loose the first few times you use it anyways so they don't feel suddenly restricted or claustrophobic by the new sensation. I bet your gelding is fun to drive if he used to be a roadster!