I'm not sure what happened but, about half of my post didn't show up.
I'll try to retype it tonight when I get home. The short answer to your question though is, P&G with the engine off isn't possible above 40 mph in a Prius. Above 40 mph the engine has to be on to help protect some of the CVT components. Again, I don't know where my explanation of my techniques went but I'll try and re-explain them tonight after work.