Hannes, I'd like to see a closer picture of your sail mount if you have one. So it sounds like there's a bit of T9 following in Wien (Vienna), any interesting forums or blogs you can show us?
I shortened a full on sleeping pad just a little bit to make the interior of the T9 very comfortable. In the picture below I am using a Long Haul Comfort Seat for it's backrest only and sitting on the pad on top of the deck. I think the Long Haul Sling Seat might be a very nice addition to the boat as the seat back would be similar to the Comfort seat seen here and there would be some cushioning to sit on without the rise (elevation) of the Comfort Seat.
I've sailed the T9 with the Kayaksailer and found it to be a good sailer. Recently I discovered that loose rubber on the stern piece was ballooning out while I paddled and sailed. So it seems I always had a bit of onboard drogue effect happening while out on the water... not so bad with the rudder but made the boat impossible to steer without. Unfortunately I had some other mechanical malfunctions which have taken the boat out of service after I discovered and mostly fixed this ballooning problem.
You can see some more of my T9 pics here in this gallery:http://www.dennisleephotography.com/Boats/Klepper/n-p9swW/i-bHRN7jt
The Hobie sidekicks work very well with this Kayaksailer rig - and although more experimentation is necessary I think the Harmony sponson system might even be better. Sailing the KS without some kind of outrigger with the T9 eventually resulted in a capsize each time I tried it.
With your sail mount up front, you might want to consider the Flat Earth Sails as well. They might give you better upwind sailing capability than the Pacific Action... it also seems to take up less space than the KS. I believe Flat Earth mounts their sail in a similar fashion to what you might have for the PA.
You might have noticed that I also replaced the wire cable for the rudder system with high end sailing line (a recommendation from another member here), I love that improvement. You can see the new line in the padded cockpit picture. The old cable in the Harmony picture.