Fairings can be pretty large and bluff body looking and still reduce drag, so I’m confident that SB>1’s rotor fairings will be an improvement over the comparatively inelegant metal structure that are the rotor hubs. Raider’s hubs are a different structural solution and fair more compactly.
I don’t think Raider is 50+ knots off it’s target speed... it was never advertised to hit the speeds of the X-2 Demonstrator. And I can think of ways that vibration can limit top speeds if the high 4P vibes leak into the drivetrain or other components that have loads that directly scale with speed. So it’s performance miss could be both drag and vibration limited. That said, it’s still a sleek airframe with one of the slickest engine installations I’ve ever seen.