Features in Urdu font

Hi there

I'm fairly new to the details of OpenType, and I wonder if anyone here can help me. Just a quick intro to get some context for the question: Urdu traditionally uses a very complex variant of Arabic script called 'Nastaleeq' (or any number of alternative spellings!) where words are written sloping downwards from right-to-left, so initial characters are small and high-up, with final characters big and swirly at the bottom. This makes it hard to specify technically, and there is no Unicode standard for the process AFAIK.

We've got a couple of Urdu fonts here, one of which uses an enormous number of ligatures (about 10,000 of them), another of which uses more standard Arabic joining rules, but with far more variants of each character. What I'm trying to do is find where in the font the information is stored for these two processes. Bringing the fonts into FontLab Studio, the features tables aren't terribly helpful - here's a sample from rlig:

lookup rlig54 {
} rlig54;

Am I looking in the right place? The fonts work great in Word, so the features must be working correctly.

In case it helps, the two fonts are Jamil Noori Nastaleeq and Nafees Nastaleeq

Thanks for any advice