That is a tough one! In an Incubator the Humidity is higher than you will probably be able to maintain in any tub or other type of enclosure. With that said I would say keep it as high as you can. Also make sure you have a good proportional thermostat heating mama's set up, but don't let the eggs sit directly on the UTH. The mother is only really able to heat the eggs up by a degree or two through tightening her coils around them. Basically using pressure to raise temp. They also do a little shaky dance supposedly when self incubating which it is not sure if this has any affect on the heat or anything else!