You don't want the ambient temp in the tubs to be 88-90. When you use back heat you don't go by the hot side temp recommendations used for belly heat or it will always be too warm and the snake can not get away from the heat. Think of those breeders who simply warm their snake room and don't use any additional heat. They don't keep it 90 degrees. That's too much. You just want to keep it slightly on the higher end of the ambient recommendation. It certainly isn't 90 degrees inside the termite mounds BPs live in in the wild.
----> Signature <----
*Factoid: "There are no such things as Hogg Island or Columbian boas"