I have a 2 door (sliding) incubator And I have a heat mat on the bottom and one on the back with 4 fans in each corner 1 pointing down ,1 up , 1left and 1 right Working well :)
Fans are just circulating the air inside and on all the time if they were turned off I might get a hot spot somewhere And what's a hot spot not A GOOD SPOT lol sorry (tv show strike it lucky)
Open once a week for fresh air and tubs
But as I'm testing our hognose beer fridge and done the work for you ;) You won't need a fan as mines 0.6 out top to bottom I've turned the fan off as it was making the top tubs hotter (strange but there you go)
Ive only got a 11x17 matt spare so that will have to do. I mite still have a play with the fans only as its sitting on a freezer so i mite get a hot spot in the bottom but time will tell i spose.