Another thing to try is insulating three sides of the enclosure. This will go a long way in keeping your ambient temps up, and will make your snake feel more secure in a glass enclosure. Also if you have a screen top, covering some of it will help keep ambient temps and humidity up, but be sure and allow for adequate ventilation and keep anything you put on the screen top away from your heat emitter. You should have no problem hitting ideal temps with the heat sources you currently have if you insulate a bit.