Hi Andi,
I have SW12 modules in use, probably the same you gonna use, and they make use of extended X10 commands to position the blinds. Extended X10 commands are not supported by homegenie. A long time ago I had some exchange with Gene about it, I haven't been successful in controlling SW12 with DIM Commands.
I thought about using the mochad driver for that purpose but had no time to investigate further.
If you like to give it a try there's a PDF added with the information like
pi@raspberrypi ~ $ echo "pl p16 extended_code_1 0 1 0" | nc localhost 1099
04/20 19:01:46 Tx PL HouseUnit: P16 Func: Ext code 1, data, control Data: 00 Command: 01
in this thread
http://www.homegenie.it/forum/index.php?topic=129.75Bests
Jens