[jonnyk]

Adding boost doesn't have anything to do with compression ratio. It adds more air and fuel into the equation. The reason you would consider lower compression to run on a given octane of gas is because the now more dense (proportional to the boost) intake charge is still being compressed the same amount, so you will ultimately see a much higher cylinder pressure at TDC than you would without the boost. Basically, this means that the chances of preignition are greatly increased prior to TDC due to the increase in mass of air and fuel being compressed. This requires taking timing out of the equation, or running lower compression, etc.
You cannot state 1 psi = 1 point of compression, there is no real equation for how much manifold boost you see to how much boost you can actually run. Every engine and combination is different and that's where tuning plays a big role.
As for destroking, I think that is highly counterproductive. 7000 revs is nothing for a solid rotating assembly that a lot of quality quality stroker kits offer. I would be more inclined to stroke an engine to reduce it's operating rev range and still make the same amount of power, given that you are adding forced induction. RPM kills engines so ideally for a long lasting street car you would try to keep them as low as possible. If you were spinning to say 9000+ rpm all motor in a race car, then you would see the argument for destroking having real benefits.