Did you end up giving it a try? If so, I'd be curious as to whether you've found the correct wires in the factory harness to tap-into the steering wheel controls, as I'm trying to install a joycon device.
I just put a carputer in an 08 9-3 Aero. I put the computer in the back left-hand corner of the trunk where the Bose amp was (replaced it with a real amp), and a 7" touchscreen in the dash. I had to fabricate my own dash for the screen as it's hard to find dash kits for these cars (and was impossible just 3 months ago).
I ended up not trying it yet. They make a wiring harness for the steering wheel controls that you can buy from the UK. I am pretty sure you will need one of those to make it work. Do you have any pictures of the mounting kit you made? I would be interested in seeing what it looks like.
I'll post a picture of the dash when I get a chance. I got tired and just painted it half-done, so I still have to fill in a few gaps and sand it smooth, but it looks not too bad already. They now sell double-din fascia kits for this car. SonicElectronix has them, but they're about $150.
Honestly, the biggest pain on this car was the stereo upgrade. Getting the amplifier power wire through the firewall is tough as it's pretty cramped under the hood, and the door speakers are a funny shape that makes it hard to upgrade them.
I'm looking for the right harness, but not sure which one I need. I think it needs to be something that converts the CAN-Bus signals from the stereo harness to resistive signals, which would then hook into the joycon. I don't think the PAC harnesses that a lot of people are using are compatible with the current Saab models. If you've seen something that might work let me know.
Thanks for the tip. I ordered one off of their website. Apparently they also convert other information from the Can - bus, such as acceleration, reverse, etc, so It'll be interesting to see if I can find a way to make use of those signals.