I have not done it in a while (like a year), but yes I get pretty good sharpness with this combo wide open and my now sold D700. Using it wide open with the TC20EIII the results were not so great . . .
Dennis, there IS sample variation with all the TC's.
Most guys I know buy several copies (used) and keep what works best for a specific lens/body combo.
Fine tune may be your best friend here, so don't give up all hope of sharp wide open...tho you'll see it
more frequently with a prime OR the 70-200 VR II