I can see my boost easily run up to 11-12 under hard load. I dont worry much about the boost level but instead watch the EGT carefully.
(My engine is a stock compression unit)

Once the temp starts aproaching the lower end of the crispy zone I get my boot off the loud pedal and allow things to cool or at least keep the temp in a safe area.

Even at 10-12 psi the aftercooler is only marginally effective.

The air to air coolers come into their own when you get to 15- 20 on up.

For lower boost pressures I would really be inclined to recommend a water alky injection setup.

This adds power, keeps the little monster cool and also steams out the combustion chambers and they will stay far cleaner.

Best

Robyn