Jim, you and I know that people who are offering the most advice here rarely know what they're talking about from experience. When they lack knowledge on a deep level, they always always always resort to personal attacks instead of making a better point. Being politically correct is soooooooooo...
Computer fans work great with exoterra's. The chimney effect maybe true but thickly panted enclosures will negate the airflow considerably, so, small computer fans greatly help with healthy enclosures. I blow air in for the optimized effect, no the other way around.
I like the idea of the 70 watt myself. Did you notice any brighter output or more surface area covered by the light between the 35 watt and 50 watt? Thats too bad about the double sided tape. I have some 3M tape that would hold airplane wings together if you need some.