H264.mov - forced CBR ?

Hi,
I have an animated cartoon digitalized from PAL DIGIBETA tape onto the mov file with the ProRes 422HQ codec.
It is an old cartoon called PEPA: http://www.youtube.com/watch?v=DCWHh_mZogE

The initial video bitrate is variable bitrate @24.5 Mbps.
I need to recompess the file into h264 with the bitrate of 6-8 Mbps.
I used Mpegstreamclip and Handbreak but I can't get the required bitrate.

In Handbreak, even if I choose constant quality @RF:0 (lossless), the output file is around 2 Mbps.
In mpegstreamclip I select H.264 Multi-pass restricted to 8 Mbps and optimized for download, I get the same output bitrate of around 2 Mbps.

I have also tried FFMpeg for Mac, with the Force Constant Bitrate option enabled and the output was the same as above.

Would anyone here know of a way to create a h264 video in a mov wrapper which would allow to set a constant bitrate of a choice?

Please help!

All the best!