In view of the above, for practical putposes, trying to get maximum
performance
out of the loaded radiator, it should be beneficial to have the same
diameter
of whip above the coil, rather than tapering whip?

That doesn't help much. What helps is a humongous top hat which does
help to equalize the current at the bottom of the coil and the current
at the top of the coil.

I know about the effect of hat, but I am refering to straight whip loaded
radiator and whip above the coil only. Forget the hats and ties.

Again:
One might deduct that if the current is diminishing towards the top, that
the
diameter of the radiator (RF resistance) could be tapered also. But since
the
RF current has to flow to the tip and then reflect and go back and interfere
with itself, we should make it uniform, where possible. (?)

Yuri