I've been surrounded by beech my whole life, but only have limited experience with them as bonsai from the few taht I've collected and had survive. But a beautiful beech is well worth the wait imo.
As with most trees, the fastest way for it to gain girth is to plant it in the ground or a large grow box. You just have to be careful when growing them out to watch out for where you want to trunk chop because these guys scar easily and don't really heal over.
Here's another link:
http://www.bonsai-bci.com/species/beech.html