I screwed something up in my base calculation.
I think what I was thinking is Base Level = Level sans parameters (R/D/T).
So, WoSW is base 20 (5, +2m Highly Unnatural, +1m Rego) = 4omph
Wizard's Leap (Base 15, 50 paces), if mastered and cast every round results in 1000 paces per diameter (one Roman Mile), which is 30,000 paces in an hour (30mph)
So for the Black Carpet, I now calculate 30mph as well (Base 15: 3, +2m Weight, +2m Speed)
And for whatever version of flight, being burdened does slow things down. Figure the carpet can carry (x) number of passangers with light burdens and travel at that speed, adjusted accordingly (as you calculate is reasonable I suppose).
And concentration is important. Carmen created her Talisman just around the concept of it concentrating on flight for her. If you check this page (scroll halfway down), you will see why.
Thinking on my above calculation (which can be tweaked when needed), I suppose we can back calculate speed per round.
Paces per hour = 1000 x mph. 20 rounds per diameter times 30 diameters in an hour equals 600 rounds in an hour.
So... (using the Roman Mile of 1000 paces)...
(mph x 10) divided by 6 equals Paces per Round.
Bae 20: 40mph = 66 paces per round (hawk in flight)
Base 15: 30mph = 50 paces per round (galloping horse)
Base 10: 20mph = 33 paces per round (something)
??: 15mph = 25 paces per round (a fit athletic human running)
Base 5: 10mph = 16 paces per round (horse walking)
Base 4: 8mph = 14 paces per round (average human running)
Base 3: 6mph = 10 paces per round (??)
Base 2: 4mph = 6 paces per round (brisk walk)
Base 1: 2mph = 3 paces per round (slow walk)