Spotted...

one for track and one for road.

but I just got a 20t in case I need to bail the DD and get to 67 GI which is really gay.

I just like to build up a selection of cogs and chainrings, to cover all angles.

It would be a really good idea to invent some kind of cluster of cogs that you could select at will whilst riding, I'll look into it ;)
gramps, i ride 67" and didn't see you much at the front on the way to oxford?!?