(different spec, same frame), do I want the rear wheel as close to the seat post as possible, or more of a gap like in the photo? Common sense says as close as possible, but I know from experience that common sense rarely applies to aerodynamics.
I think the answer is "it depends" (on frame, wheel and tyre combo) - wind tunnel or some kind of aero field testing is needed to determine the optimum
On a Dolan DF4, like this:
(different spec, same frame), do I want the rear wheel as close to the seat post as possible, or more of a gap like in the photo? Common sense says as close as possible, but I know from experience that common sense rarely applies to aerodynamics.