Ok thnx.
Thought I might have to run a shell script to load, wait, and then run the app but notice that a script does that from the ondemand directory - the vlc command now calls the script in ondemand which loads the extension and then runs vlc for real this time. Clever.
It is a matter of deciding which is to be preferred - a slow first run time of an app or a slower boot time.
On the whole I think I am quite getting to like tc.