Just bumping this thread as it may prove useful to others. Just put new boots all around on the GTS having run the rear Pirelli tyres at the handbook recommended lower pressure of 2.0 and looking at the old tyres I would say that they have worn pretty evenly across the tread pattern. You could say the outer quarter has worn more than the rest but not a lot in it, so it seems it is OK to run at this lower pressure for the MC Shift cars.
I got 8k out of the rears, the fronts could go further but decided to change them anyway due to inner edge wear and slight tread cracking (pretty poor for tyres manufactured only 2 years ago and 16 months on my car).
Hope this info might be useful for someone!