> I am sure from empirical means that the effects of intertia are very small.
In the case of circling in wind I agree. The rate of change of heading is too low.
..but it's worth remembering that if inertia didn't exist you could make a flat turn using rudder only with no skidding.
..or to put it another way that 45 degree bank is only needed because of inertia. That's half the lifting force of the wing needed to counteract it. Not so small eh?