Testing 300/4.0 L IS

Greetings to all participants of the Forums,
I am doing wildlife photography and I am newer in the digital photography.
Recently, I bought new EOS-10D, 300/4.0 L IS, the both Canon extenders EF1.4x II and EF2.0x II and the Speedlite 550EX. I did lot of pictures to recognize the camera, but I am not fully satisfied by the sharpness. I am not sure the Imige Stabilisator is working properly, and the lens sharpness is enough good. I have too EF 24-85/3.5-5.6 USM lens and it has perfect sharpness, never mind it is not “L� marked. I will appreciate very much your advice how I can test the Stabilisator’s work and the Lens resolution?
P.S. I bought them as new items from B&H.
Best wishes,
Valentin Potchekansky
Bulgaria

Post a sample of a shot taken in good light along with the full Exif.

The 300 F4 is an excellent lens, very sharp and a lot of contrast. You are aware AF will only work with your camera with no TC or the 1.4? You will have to use manual AF for the 2x TC (forget about taping the pins, it hunts very slowly for focus).

Without an example of what you are talking about it is impossible to help you.

Thanks Kenny,
How I can post some pictures and where?
Regards,
Valentin