I am not sure on the 987, but on the 986 the front maxes out around 1.7 to 1.8 degrees of negative camber, so you will be swapping suspension parts out to get more.
I would look to see if you can find any of the Pirelli Corsas. I can't get them in Canada anymore, but if you can find a set for the car I would recommend them over the MPSC. They are a little bit slower, but far more progressive in their break away which makes them a better learning tool (and more fun for lapping days... I am happy to go a little bit slower with an easier drive... guess I am getting old!
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All that said, I would look at a good track alignment first before going crazy with r compound tires... There is a huge improvement in handling, but you still get the better feedback from the summer tires.
Marc