I am facing a similar dilemma on my engine (although different, priciples the same)

120psi per pot, whats that going to be, at a rough guess 7.5-1 CR, or even lower?

If your going to be running up to 18psi, i see no reason why you couldnt use a higher octane fuel if you feel your going to get detonation by reverting back to standard compresion. 97-98 octane readily available and Millers Octane Plus also useful to get it to close to 100 octane at minimal cost.

I assume the stock CR is something like 8.5-1? This is the same as mine. It will obviously limit you to future boost increases though but if you want driveability (like myself) then you have to make a compromise and find the power elsewhere than just increasing the boost, like ported head with bigger valves, different cam, getting the inlet temps down as low as possible etc. I realise that different engines will behave differently with regards resistance to detonation, my engine doesnt even have 'squish' to worry about because its a flat top heron head, the CVH will of course be much better in this department with a well designed combustion chamber in comparison but not being an expert with this particular engine i could say, only going by common sense.

I have a Cossie 4x4 turbo on mine, when the engine was wire rung with the intention to run high boost, the block was skimmed Anyway, this raised the compression 0.2 over stock leaving me at 8.7-1. When i first got the engine back on the road i was getting det problems at a mere 13psi, occuring at peak torque. I put this down to the slight compression increase but it actually turned out to be a dodgy gone off batch of super unleaded!

I have now gone up to 17psi without detonation problems but as a knee jerk reaction i had Mike at Ferriday make me a de-comp plate, sufficent to lower it to 7.9-1, as this would make a noticeable different to off boost response i wanted to avoid this at all costs but had it done anyway.

Now, knowing i dont have det problems and limiting myself to no more than 18-20psi boost (my turbo only has a 270 bearing) i dont want to compromise any of the driveability and will be quite happy at 250-260bhp . So for this reason i wont be lowering the compression now.

Others will say keep the compression low but i would say no if you want a fast road car, lowering compression these days is the wrong route for extra power, it's all very well for a drag strip car but how often do you drive at part throttle on the strip , modern day turbocharged cars run 9.5-1CR without problems because they are mapped to do so and this is the key.. there are other factors aswell