Hmmmm. 9mm in a well collimated scope should be fine - depending on seeing conditions.
Also you don't need dark skies. Jupiter swamps skyglow!
My only comment then is are you sure you are looking at the time the shadow is on the planet, and not just a time when the moon is in front of the planet? The shadow trails the moon a reasonable amount at the moment. Perhaps use the software Jupiter2:-
http://astrosurf.com/rondi/jupiter/
Several people say this is the best Jupiter software. Make sure you have the orientation right and aren't looking for a shadow towards the bottom of your image when it's actually at the top!
OK, I've just checked. I make it Europa's shadow at 6:46pm. Perhaps look for an Io shadow transit (around 9pm 17 August, I think). It's closer to the equator - might be easier to see?
You'll get it, I'm sure. I saw a double transit and the seeing was average, so the shadow would come and go in visibility. As Jupiter drifted across my field of view it would snap into place, then vanish again.
Here's the thread where I and others discuss this - and some photos:-
http://www.iceinspace.com.au/forum/s...ad.php?t=21110