There can be probs with the internal RoBo method, but works for some. I use to use it but just do VBR 1 pass as per the tute and they only take 3 hr for me. 2 pass is for 2 1/2hr movies or more.
The Q factor changes the file size, try 40 then. A lot of fidling to get it right actually thats why I think they made the Pluggin.