[templar]

It is the smallest and it has a tendency to seep out of whatever storage container it is put into.

There is a time factor as well as a seepage factor to consider here. The storage need not be for extremely long periods (gasoline aslo has a tendency to go 'bad' over a period of time). The Hydrogen only needs to be stored in a manner that will minimize loss during the period from manufacture to use. This could mean only a few weeks of actual containment without significant loss is needed.

[Constantine XIII]

There is a lot of work being done now to fashion a container out of carbon nanotubes. The hydrogen would be suspended in a substrate of the nanotubes, so that even if the tank was split wide open it wouldn't all escape at once. Nifty stuff, those nanotubes.