Since no one else wants to offer any advice here is the info you require.
Fill the empty void in the bottom with styrofoam, it is just a nuisance.
Once you have leveled out your floor you need something to create a sturdy bottom. I used leftover kitchen floor tiles to make myself a solid base for my flexwatt.
I then used 3' of 11" heat tape which was just enough to run the length of the floor and a few inches up each side.
You will then need a computer fan and place it on the heat tape in the center. You will need to make a stand of rit so it is not touching the tape itself. Also make sure the fan is blowing upwards, this will help heat the upper section quicker.
Herpstat probe outside the egg box and try to keep above the fan open so the air may travel freely.
-Steven