Once I started lowering the temperature when I raise the humidity I never had a poults drown. You can get it as high as you want. Have you tried it that way?
Page 26 is on incubation of turkeys.
http://albc-usa.org/documents/MasterBreeder/turkeys_combined.pdf
Incubation
Poults can be hatched naturally or artificially. Some producers will use broody hens to hatch eggs but this will limit the number of poults that can be hatched. A more efficient way to hatch large numbers of poults is to use an incubator. These machines come in many shapes and sizes.
Before setting eggs, regulate the incubator temperature and humidity and let it run for 2-3 days. After that, allow the eggs to reach room temperature before setting eggs in the incubator trays, again with the little end down, big end up. After eggs are set, the incubator temperature will drop but soon thereafter the incubator will return to the desired level.
Recommended hatching temperatures within incubators vary depending on the type of machine being used. For the more commonly used forced-air incubators, the recommended temperature is 99°-100°F for the first 22-24 days of incubation. For the last 4-6 days, the temperature is reduced to 97°-98°F. The recommended humidity is 60% for the first 24 days of incubation and then 70% for the last four days.
To check on the progress of the embryo, candle the eggs after 7-10 days in the incubator to check for clear eggs or blood rings, both of which indicate dead embryos. A high number of clear, undeveloped eggs could mean infertile toms. High numbers of blood rings could mean unhealthy or old breeding stock. Remove the bad eggs to prevent them from exploding from bacterial growth and contaminating the other eggs in the incubator. Candling is also a good way to check progress in the eggs as they further develop. With appropriate temperature and humidity levels, the air cell within the eggs should become larger over time as described in this image.
Three days before eggs are scheduled to hatch, they must be placed on their side in the hatching tray. At this time, lower the temperature and raise the humidity to the recommended levels to facilitate hatching. After poults hatch, leave them in hatching tray for 24 hours to dry off before moving them to the brooder.