I have read that a solid cam will act 10* smaller in duration compared to hydraulic. My old 484 seemed a little tame ~242*@.050. The Hughes solid is 256*/260*@.050, or act like a 246*/250* hydraulic. Am I looking at this right, or do I have it bass ackwards?

That is about right for a .020 lash solid cam.

For duration measured at .050 I understand that a mechanical would have a wider RPM range compared to a hydraulic with the same duration. The mechanical works like a slightly smaller hydraulic at lower RPM and works like a slightly bigger hydraulic at higher RPM. I took a look at Hughes web site and the 5660 mechanical lists an operating range from 2800-6600. The nearest hydraulic is the 5561 which shows an operating range from 3200-6200. The mechanical has a little more down low AND at the top end compared to the hydraulic.