how do I grow Cathea?

I was recently given a Cathea edulis and told it was a slow growing plant and best kept indoors. Well, in 1 month it has grown about 6 inches (so not that slow) but the leaves at the bottom of the plant seem to dry and fall all the time. There is about 3 inches of bare stem at the base now. The rest looks healthy. Also, as the leaves mature they seem to curl slightly. I've repotted it into cactus compost as I was told it needed a free draining medium and I only water it once a week. It is on a window sill facing south west.
Should the leaf drop be something to worry about?
What should I do about the slightly wayward new growth? Its bending quite a lot and looks like it may break.
Help!
Luke

 

Do you mean Catha edulis? Otherwise known as Khat, Ghat or Qat?

 

Yeah. Thats the one. Clumsy fingers on the keyboard make for bad spelling!

 

This plant comes from arid parts of Africa. Leaf drop is the first sign of overwatering. Use a fast draining soil--ie. 1/2 potting soil and 1/2 perlite. Good lighting is also important.