Solved

I'm glad to say I understand the SG.DAT file now, and have created my own rain shape. I've adapted it a bit to simulate the effect of a falling drup. That means it starts slowly and then starts to accelerate on the way down. It uses 50% of the entire tilt range, since that gives the best effect (though offcourse that value can be changed). It's created for yokespots, so you shouldn't set it too fast since the yokes won't keep up with that and the effect isn't going to be what you would expect.
To start the effect; simply set the yokes in the centre of the movement (thats half way down) and start both plsFade and the rain shape. Set speed to max. 40 and program onto a playback. Dimmer should be set to 50% for the entire dimming range.
Link to my SG.DAT:
http://www.lichtbron-oo.nl/SG.DAT
Editing the SG.DAT gives a lot of options, but isn't that easy as one would think. Thanks to niclights for helping me out with some problems! I would like to ask developers at Avolites why the pattern creation is set up like it is. It's not an easy way to go, I could easily come up with some other ways of acheiving the same results without having to think as much as I had to. Please let the CPU's do the thinking, there much better at it
In my opinion, the shape generator should work on a percentage based system. That way, 100% stays 100%, and doesn't require the user to set the channel value at 127 to acheive the desired effect. Also, there should be somekind of guide on howto edit the SG.DAT file. I used an Excel spreadsheat for calculating the values myself, I'll post that as soon as I've got that cleaned up.