Get rid of the Human heat pad. If you want to use a UTH get a UTH they are designed for that exact purpose. A human heating pad was not designed for that use, they are very unreliable and I would also think it would be a very inconsistant heat source. You can pick up a decent UTH at any Petco or PetSmart. Also I would not suggest replacing the plastic top with mesh or screen. It will probably give you humidity issues. Allowing most of the humidity to escape. That also depends on your environment. If you live in a very humid area that may not be a problem but if you live in a very dry area this could be an issue. Screen or mesh would also make it hard to maintain a consistant temp. Just my 2 cents