When using an LG I can't stress the importance of a wiggler. What people call BIG
temperature swings are usually their thermometers registering the heaters turning
on or off.
The key is egg temp, and that is what a wiggler tells you. An oral thermometer in
a wiggler or in a cup of water will tell egg temps. A hen maintains egg temp by contact
with her body. A broody hen is a lot more than a big puffy blanket.
Mass is also important. Putting 12 eggs in an empty still air 9200 will cause more
variances. Keeping air a stable temp is hard. It's better to put water bottles in the
empty spaces to help hold the heat.
As for humidity, like Poulets mentioned, if you put a few paper towels in the base
with a corner in the water wells it will get humidity up quick. I usually cover the
whole base, not the vent holes, with the towels and let the humidity spike. It's
easier to manage high humidity than low humidity. I use this same technique with
my
Brinsea.
If you can add a fan kit it helps a lot.
And never open the bator after day 18. I have messed up a lot of eggs by being
impatient.