If any wall, floor, roof of the enclosure is of mesh, there is no real answer. The heat and humidity will waft out because warm air rises, pulling cold dry air in behind it. Cold and dry is a good human environment. We need to keep a bubble of tropical environment for our iguanas.
So for now I'll assume your cage has some mesh walls. If not tell me so I can change my answer.
Your iguana physiologically needs one place that is hot (95F at least, I gave mine 105F) and has UVB, that he can fit his entire body into. He also critically needs a place that is cool and dark. Dark in the sense of under a leafy tree. To digest the fiber in leaves into carbohydrates, igs have a colony of symbiotic "gut bacteria" that they keep alive by eating leaves to share with them, and keeping them warm so they can remain in high numbers.
Igs will automatically bask and need to get literally hot, to boost their gut fauna/flora. Their bodies tell them when they need to withdraw to a cooler place. They cycle from cool to hot several times per day. They would die if it were not possible.
So, that shows that in your habitat, there are two ends, one hot, and the other cool. They must be separated far enough to not interfere with each other.
The compact UVB has been proven in the recent past to be dangerous for reptiles, causing eye inflammation and swollen drooling eyelids. If the manufacturers say they have solved that problem, I still would not buy one until I had read lots of good reports about them. They also shed too small a circle of UVB, being good for only small lizards like anoles or Western Fence Lizards.
I don't know what a "strip fluorescent" is. I'll assume it's a fluorescent tube that emits UVB. You have to get the right kind, and they can't be too far from your ig's skin. A 36 inch ZooMed 10.0 works well. In the past, ZooMed's 5.0 was the first UVB emitter that allowed captive iguanas to survive. That was back in the 1950's I think. The 5.0 is still dependably able to support your ig well for even a long lifetime.
This fluorescent needs to be all the way to the end of the cage at the hot end. So it does not extend toward the cool end. I always place my tubes near the back wall, so they could bask farther away from the front, helping them to feel more secure and induce relaxation. This is a help for the less secure iguanas.
You have to place the 10.0 within 4 to 5 inches over your ig's back. I used to place them 4 inches above the substrate. That put them one inch above the top of my igs' backs. It never caused any problems, and assured adequate UVB. That is totally safe for their eyes and skin. UVB dissipates drastically over distance. If you mount it near the top of the vivarium, your ig will receive zero UVB, get sick and die.
One of the 36 inch 10.0's or 5.0's is enough if used as I described. A 36 inch tube seems ideal. as it will irradiate the hot end of the viv, and not shine light onto the cool end.
I have a small native lizard in a large glass tank (blea, I know, but he's small). The only UVB I have are 30 inch HO T5's which span the width of the tank and so illuminate the entire width of the tank. I have to box off the tube where it extends into the cool zone, to block the light so the creature can get away from the fluorescent light when it wants to. I have a Zoomed 15 inch Iguana Light 5.0 UVB F14T8, which is just right for this little guy, but I need to order a special $9.00 + shipping ballast for it. For now, I'm short on money.
Well, I hope my comments answered your questions.