agreed. That is the place to be. I did part of a fuid mechanics course as part of a chemical engineering degree I never finished many, many years ago. Pretty heavy duty math but really interesting. Forgot it all now. My memory for surface integrals and whatnot is pretty poor lol!
Back OT, i do use 3mm coils quite a lot but they do certainly work best with a decent AF aperture for the reasons you state!