[color:"red"] "Helium is an ideal/inert gas, so, truthfully, He2 is not really stable" [/color]

Right, it's NEVER been seen under terrestrial conditions, ever. You're right about He being small and a ballon is porous to it.

However, your comment about H2 not being used anymore, here's a bit in use. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />