Heat pads and rubbermaids

[Cas]

It's late, I'm tired, sorry if this doesn't make great sense.........

Does anyone out there have any experience with Exoterrra heat wave heating pads on rubbermaid containers? Are they suitable, or should I go with a "Wal-mart special" (human heating pad)?

I haven't actually used heat pads with plastic containers before, so I'm wondering what the method is...... I imagine that I'm going to want ventilation on at least one side of the heat pad to avoid overheating and melting. Now, the question is do I set the rubbermaids directly on the heat pad, and set the heat pad on something ventilated (for example, a wire baking rack).... or do I set the heat pad directly on a surface, and then elevate the rubbermaids an inch or so away from the pad?

Also, in the case of the 'heat wave' pad, do I have to stick the pad to a sheet of glass or something (I do not want to stick it directly onto the rubbermaids I'm using), or can I just leave it "unpeeled"?

(A thought..... why doesn't anyone produce a reptile heating pad that DOESN'T have a sticky backing??)

Thanks,
Dawn