"Jeff Findley" wrote:

If we're talking about the same flight profile (carrier aircraft lifts
hybrid powered spacecraft which is dropped and ascends to 100 km), what
would need to be different, aside from scaling the design up by a factor of
two?

Refinements for even faster turnaround than SS1. A significantly upgraded
passenger cabin, with "comfort" features (like a vomit vacuum system) and
lots of video cameras.

More windows.