On the incuview. I have not tried duck eggs. Just large chicken eggs. Seems large enough for duck eggs. The slots are pretty wide. As long as the egg is touching the bottom screen they should turn. If not with some skillful trimming the slots could be widened a bit.
Some people take the turning tray out for hatching. The eggs will roll around a bit once chicks start popping out. I leave the tray in. The motor stops turning for the hatch period, but I usually take the arm off just to be sure. Have had good hatches and no issues. It even did well with shipped eggs even though they have to lay on their sides. Check the fan after each use. It really collects a lot of fuzz.
Some people take the turning tray out for hatching. The eggs will roll around a bit once chicks start popping out. I leave the tray in. The motor stops turning for the hatch period, but I usually take the arm off just to be sure. Have had good hatches and no issues. It even did well with shipped eggs even though they have to lay on their sides. Check the fan after each use. It really collects a lot of fuzz.