depending on how long he's been on live, he may have imprinted on it. you can feed him two of the smaller sized rats, like rat pups to get him conditioned to taking two prey items per feeding. then offer the first live, then the second pre killed. after 3 or 4 feedings, offer 2 pre-killed rat pups. after 3-4 feedings, offer 1 pre-killed, and one frozen, then repeat the same process until you get him eating on 2 frozen weekly, then you can bump up your prey size.

But first I suggest that before you even start thinking about switching him over to f/t, get your BP eating live on a regular basis.

Hope this helps