Jimi,

Telling you the truth, if you want to delete free data tables, you have to make sure a couple of things.

1) data integrity
2) data dependency
3) is it completely not used? (or is it only partly not used?)

I think the best way to do that is to backup the database and start removing stuff you don't think you don't need.

BTW, I am in HK now too :)

Ciao,
Tom