Hi, i don't know about the polystyrene rock stuff but i think its a cool idea.
As for lighting....because all of my geckos are in a basement room with a very small window i like to provide a day/night schedule. This i'm going to be doing with tube lighting instead of individual lamps on each tank (i have way to many tanks LOL and plugging in UTH's plus lights is eventually going to overload the circuit). So one clear tube light will run along all of the tanks while a second red coloured one will do the same, both plugged into timers. Only during our Great Canadian winters do i supplement with lighting for heat.
In my opinion, a UTH is just fine to use as long as it keeps the ground temps correct.
Now in regards to moving him.....of course he'll be fine. Like was already said, just don't bug him for a while. I just moved my 4 newer girls (bought beginning of March) into a 40 gal tank. I've seen alot more activity from one in particular than i've ever seen and i'm only going into the tank to feed/water/clean. Oh and to check the humid hide as it appears Flame is going to lay eggs again soon.
I think more importantly when designing and building an enclosure the things to consider are: adequate air flow, ie. screened top, making sure the UTH has space to ventilate excess heat and security...you dont' want the geckos getting out or anything getting in (cat for example) 
I hope that helps i look forward to seeing your setup
Red
>>I recently bought a 5-6 month old gecko about a month ago. I have him in a 20 gal terrerium with sand substrate right now. I want to move him into a custom built cage but am not sure of the demensions quite yet. Definitly much bigger than what he has now. The following are a few questions I have concerning building him his own custom cage.
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>>1.) Is it ok to use the polystyrene rock idea with leos. I don;t really think this would be a prob but I was wondering if anyone had their leos on this and if there were any drawbacks to using it.
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>>2.) What should I use for lighting. I was thinking of putting in a lightbulb and a moonlight as well. However, I would like for it to be hotter on one end of the tank at night. Somewhere around 80-85 degrees. Would a blue or red light produce this type of heat. If not should I get an infrared bulb(think that is the proper name) or would an UTH work as well?
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>>3.) Lastly I want to know if I should even be considering moving him because it might cause too much stress for him to adapt to a new enviornment. Like I said he's only been in his tank for about a month but it might take at least another 3 weeks before I complete his new enclosure.
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>>Thanks ahead of time for any information or comments regarding my questions.
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Crested Gecko Zeek:1.0, Ziggy and Zeus
LEOS: Boo: 1.0 normal , Bronx & Nala: 1.1 blizzard,
Lily: 0.1 patternless, Abby: 0.1 albino, Zoe: 0.1 reduced pattern, Dot: 0.1 hypo
New Girls: Flame, Karma, Bubbles and Bell pics coming soon
Chip: 1.0 papillion (small dog)
