We are to begin installing sill plate tommorw but after checking for levelness found the foundation to be high 1 1/2" more in some areas than others. Also the center wall that will support the mid span of I-joist is at least and 1" or more higher than the perimeter block. Would you try to shim this out? Seems to far out to me to even attempt to shim. How do you try to level a foundation wall this far out?