Float the raft with loads of aeration,in Hydroponics with no pump or aeration the raft is allowed to float on the surface of the nutrient solution when the raft is planted with seedlings,then as the root find the nutrient and take up the water the level reduces,it then comes to rest on supports so as to leave an air gap between the raft and the nutrient.This way you grow air roots that aerate the plant,so there are two trains of thought,aerate and float the raft or don’t aerate and supply the air gap by lowering the water level and supporting the raft.
If you aerate and lower the water level you end up with a mist above the raft that drenches the roots.
