Make a viv 4ft or bigger
Up to 4ft 100w is fine
Bigger 150w would be better
So long as its on a thermostat it wont over heat.
It would be a lot better if you have a solid roof you will need to change your holder to one you screw onto the wood, and you will need a cage more to protect you from burning yourself.
Cut out a circle and cover it over with mesh, small squared mesh is best. 4ft you need 4 vents.