Lay the wood floorboards in place along the edge of the thicker flooring surface. Measure the difference in height between the top of the wood floorboards and the top of the thicker flooring surface. Do not rely solely on the difference in thickness as noted by the manufacturer. Take your own measurements as variances in the subfloor affect the actual differences between the two installations.
Lay down multiple layers of felt underflooring as you would in your typical installation. Leave 1 to 2 feet of additional length near the edge of the seam between the hardwood flooring and the thicker flooring material.
Fold back one to three layers of the felt at the edge of the seam for the two flooring materials. Lay the hardwood flooring on top of the layers and then check the remaining distance between the two materials. If additional shimming is needed, lay down an extra piece of felt to raise the flooring. If less shimming is needed, fold one of the layers back and cut it flush to the thicker flooring.
Repeat this process in any area where the hardwood floor needs to be raised.