'86 951 best tire pressure

[paul r]

Porsche say my car should run 36psi. I've done this for the last 7k miles. The result is that the centre section of the tread has worn about 50% more than the outsides. I don't have any geometry problems. Now I reckon 36 is high for such a car. I am also aware that in the 70's Porsche experienced accelerated centre section wear on high speed autobahn cars using the first wide (by todays standards) tires. The factory countermeasure was to increase tire pressures to stop the centre section of tire flexing out under centrifugal foreces caused by high road speeds.
So I wonder if 36 is to prevent the above situation. In my case my average speed is around 40mph (unfortunately). In which case would i get better tire life and maybe grip at lower pressures.
Your experiences would be appreciated.
Thanks
paul R