I would suggest turning down the input trim a little since you're using HB's. Also experimenting with IR's as mentioned.
Not sure about the ultra as I never tried one, but the current FW in the II really does nail a lot of the amps modeled, good points and bad. It might be that the Deluxe Reverb in the ultra is a good bit different than what is in the II now, so you might have better luck with another amp, at least for buckers. On the real DR's I've played/owned, clean chime with Buckers is not what they do well, in my opinion anyway- they tend to breakup and compress pretty quick, where as they do the clean chime thing much better with single coils.
Maybe try the Twin Reverb model.