So all bets are off.
BTW, I find your math correct to an order of magnitude for a cirular orbit.
/johnny
Circular. I am also chasing a bit of FOD around the keyboard.
The 1.08 ratio will apply to the semimajor axis of an elliptical orbit, which has to have pretty low eccentricity to stay clear of the atmosphere. For low eccentricity, the shape of the orbit is very nearly a circle with its center displaced from the center of the earth by 1/2 r*e ( r*e is the distance between the foci of the true elliptical shape. ) This means that the length of the orbit is very nearly that of a circular orbit, as calculated, and the calculated speed will be very nearly the average orbital speed.