Miles, can the Bilstein B4's be used with a stiffer drop spring. It's great to hear that Bilstein maybe providing some Focus options. The last time I checked the Bilstein HD (aka yellows and B6) were just becoming available as well, but they're also considered an OE replacement shock (although a VERY good one) and not intended to be used with drop springs.
Geezer, the B4 appears to be a OE replacement option as well. I admit that since we don't carry it I know little about it. But I would err on the side of caution based on the information Bilstein is listing and wouldn't match it with lowering springs. Good catch.