When people want to accommodate a higher-stack headset, they sometimes mill a bit of the head tube. Depending on how far the lower pressed-in race sleeve extends into the head tube (some are like 10 mm, others more like 6), maybe you could have a spacer made (30.1 mm inside diameter) that would fit between the race and the head tube bearing surface. If a machinist made it, you could even have the outside of it radiused, like the bead on some of the old Nervex lugs. Of course, what you add on the bottom, you have to give back on the top!