Exo terra 36x18 plastic cross and heat lamp

I have the same enclosure. I run a 75w basking bulb and a Reptisun 24" T5 10.0 UVB.

What I did was mount the UVB hood/light fixture inside the tank using the middle crossbar on that screen with XL zip ties from Wal-Mart. It's not exactly possible to get the UVB and Basking right above the basking spot. It's going to be a little offset given how they made the top (dumb design)

and all you need to not have to worry about burning the plastic is a 5"-5.5" dome lamp.. that's what I use. I've seen them in clamp style, with/without dimmer, or just plain on/off.. otherwise great enclosure.. just silly screen top design.
I have changed it up since taking this picture..took out the background, switched to non adhesive shelf liner, and I put the basking light on the back right corner and arranged different pieces of cork bark and decor to build like a little mountain to get up close to the UVB/Basking Bulbs.. I can get more pictures if you need them

You want a piece of decor directly under the UVB 12-15 inches -- it wont matter if its right w/ the basking bulb -- its optimal but I would get another bulb like a low watt basking bulb 50 or 75 w/ dome or a regular house hold bulb like a 40-60 watt NO LED's -- to keep the middle of your tank in the 90's it will be like a second basking area for him and then he can sit under the UVB and the heat lamp as well --- make sure you have your digital probe thermometer

I've had some luck putting foil over the plastic pieces where they come close to the lamp. I eventually started hanging the fixture from an adjustable lamp stand a little bit above the top of the enclosure, but I remember having the same issue and a folded over piece of foil cover the plastic kept it from melting.