I know I am in a shameful delay: here is the first tutorial movie, which explains how to deal with object scaling, and match objects so that they fit properly.
After I recorded the movie, I realized the capture size was set at 50%. Damn.
I do hope anyway it can be useful. Will be more careful with the next ones…
Here is the kink to the Youtube movie: http://youtu.be/NPTF7vmSSh8