i've just put shaile in the bottom of mine ( very small peices of slate ) to aid drainage and help with damping down in the summer , So i think you have done the right thing.
I'm of to fit guttering and auto vent today.

__________________
---) CARL (----
ILFRACOMBE
NORTH DEVON

a seed planted today makes a meal tomorrow!

www.freewebs.com/carlseawolf

now in blog form ! UPDATED 01 / 04 / 08