Hmmmm......
Mike, I've not participated in a traditional driven shoot but many, many tower shoots. I've read reports of good results at traditional driven shoots with #7.5s or #7s (British #6).
Makes me wonder if driven birds aren't alot closer. Perhaps the towers I've shot are atypical. Whatever. #7.5s are woefully inadequate for any of the towers I've shot....even on a day when the birds weren't flying well...unless I intended to seriously restrict my shot opportunities.
I would go with the B&P Hi-Pheasant in #5 (US #5.5). I've used this loading at towers and found it works well. Right now B&P are selling Hi-Phez at discount ($70/250, shipped).
That said, I do better with a 391 Sport and heavy US #5, or even US #4.
Sam
