I have been thinking about your original post and there are a few things you are reading that I think are hogwash. I don't know much about turbos but I do run a 6-71 blower. The 6 lbs of boost limit is a joke. I have a static compression ratio of 8.1 to 1 and I run 9 lbs of boost with my timing locked at 31 degrees. The engine loves it and so do I. With a turbo it all comes down to timing management. My solution would be to start with timing based on the amount of boost you are making at any particular rpm. You may have to pull timing out a fair amount at high boost and then sneak up on it slowly until you find what your engine likes. The other problem you may have is with 15 lbs of boost you may get into a situation where you have to O ring the block. I don't know much about that either but with 9 lbs of boost I pushed out a head gasket last spring. Just a thought.
Jack