I'm planning to use this as a guide line https://beardies.dreamwidth.org/2145.html
If you have built your own enclosure, what fixture did you use for the basking area?
I would use a PAR38 halogen flood light. They are dimmable so you can fine tune the output using a lamp dimmer or dimming thermostat. That helps when the ceiling is fixed like that. I also advise using a different configuration for the vents. Put a vent low on the cool side and high on the warm side. That will allow for some convection movement through the vents. You may or may not need the back vents at all. I would also build it slightly taller if you can. The extra height will allow you to build more in terms of climbing areas.
I'd use a regular ceramic base screw in type fixture and wire that to a dimmer. You can just get a manual dial type dimmer that you could mount on the front of the tank or go with a more robust programmable one if you want. Put that on one side and then put a T5 24'' UVB fixture next to it (for a 22'' bulb) so you have them both over the basking area.