Tripod QR plate help!!!!

[Crackson]

So I have a 5D mark 1 with the canon 24-70mm f/2.8L and when I flip the camera vertical on my Benro travel angel, the camera starts tilting down, even though the QR plate is tight on the base of the camera. The ball head holds it there, but the lens starts creeping down.

Any solutions aside from getting some silicon padding and gluing it to existing, whatever, on the QR plate?

Thanks for the help!

[Mt Spokane Photography]

There are camera plates made specifically to prevent this, check out the Kirk website.   
 
A "L" bracket lets you turn your camera to portrait position with no danger of slipping.  Its the best solution.  http://www.kirkphoto.com/L-Brackets.html
 
 
There are also plates with a ridge that prevents the body from twisting.  Look closely at the photo and you will see the ridges along the edge.  This means the plates are camera specific, and a different one is usually needed if you use a grip.
 
http://www.kirkphoto.com/L-Brackets.html