Hi there
Been a long time viewer of this site (since MMowned), and I thought I might aswell start contributing.
In IF, right above the entrace to the King, there is a ledge you can land on. From here, just mount-jump through the wall, and you're good to go!
Its a bit tricky to get underneath Eastern Kingdoms, as you have to fly a bit forward, then straight down. If you fly to short, you'll end up falling down into the kings champers, to long and you'll end up in the bank room.
A small find, and there is perhaps easier ways to get down underneath, but hey... Im contributing atleast!
PS: I'll post screenshots if anyone wants, when I get home from work.