A trick I've been using to help keep temps more stable is to use a "seedling mat" (for example: 
http://www.amazon.com/gp/product/B002LVU4Y8/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1 )
 
First lay down the mat, then a 12x12 floor tile, then the incubator on top. 
 
I started doing this to help buffer the temperature swings in my house.  Since we heat  only with a wood stove the room temperatures can fluctuate 20+ degrees in a 24 hour period. 
 
Since doing this the temps in the incubator have been much more stable, usually +/- 1 degree.