I am a chicken newbie, but I have found out the hard way that you really should not open your incubator at all during the last 3-4 days of incubation. That's why they call it lockdown. If you remove some of the rails of your turner, your hatching chicks could get injured under the turner. The only way to keep turning the younger eggs and not turn the hatching eggs would be to set the younger eggs in egg trays and tilt them. You could rig something that would do this through the hole in the top. But the humidity will be a problem too. Too high humidity will be bad for your younger eggs. You could try like 50-55% which might be ok? Decide which eggs are more critical to you and side with them. Overall, your best bet is to have 2 incubators.