I am by no means a seasoned hatcher or have much experience with the different kinds of incubators, but I too have a Little Giant.
I got one because it was a cheap way to try my hand at incubating, and I don't intend to hatch a large volume of chicks.
I just have the bare bones, no fan, no turner and a temp/hydo from
Wal-mart. I have mine in the spare bathroom that is on the inside of the house with no windows.
Same thing, I notice I can get the temp regulated but then when I put eggs in it lowers. I think it's the addition of more mass that causes the temp flux. Someone on here last year suggested to buy a dz eggs at the store and put them in the incubator and regulate the temps with them in, then switch the eggs out. I also heard that putting in little containers of sand or rocks will help with the temp too. The more mass, the better, I was told. I keep a few rocks in the incubator now, and have set it with store eggs in it. It does seem to help the temp. But I have adjusted the temp after adding eggs.
I was warned that you sort of have to babysit this model and I have found that was true. It just happens I have a more flexible schedule and I am able to keep an eye on things as needed. I also have had some great hatches in it, been pleased. My eggs I have gotten shipped I haven't had the greatest luck with, but I always add in some eggs from my own chickens to see if it is the shipping or operator error and my eggs hatch fine! I used it all last summer and now this year and I have had great success hatching many kids of chickens, ducks, guineas, and also the latest was a goose egg.
The temp dial is super sensitive and I know if I touch it I need to keep an eye on it every 10 minutes for the next hour, so I don't touch it unless I know I am there to monitor it. The less messing with it, the better, but if the weather outside fluxes a lot as it does here in the spring, it is mirrored in the incubator. I have slept on the couch several night just to be able to get up and check on things easily! You sort of have to watch the weather report and know if its going to be a warmer than usual day, keep a close eye on the temp. Same thing if they are calling for cooler weather, good indication that you need to watch the temps!
I have had great hatching in mine, but yes, it needs an eye on it to make sure things are running the way it should. But now I am in the market for something a little better, a set it and leave it type model!