Twenty Eleven Theme Header Transparency

Hi,

I was wondering if anyone could help me.

I’m using the latest TwentyEleven Theme for my site and am desperatly attempting to get the header image to be transparent and allow my tile main background image to come through.

I have saved my Header image as a .PNG 24 with transparancy at the specified dimensions required for the image of 1000×288.However when it’s applied to the site it will either have a black or white background behind it,depending on whether the dark or light theme is selected.

I have tried to root through the CSS using Google Chromes Developer tools to hunt out any background color settings for the header but am getting nowhere!!

Please someone be a hero and save me another 6 hours of banging my head against the wall and help this poor soul!!

Thanks in advance.