>>MDF I think is short for Medium Density Fiberboard. but im not sure so dont hold me to that.
That is correct.
>>Chris, would i attach the heat tape to the foil tape then directly to the PVC?
Yes, the foil tape would be used to attach the heating element directly to the underside of the PVC floor.
>>If i stacked 5 or 6 of these on top of each should i put a spacer in between the tops and bottoms of each cage or directly on top?
I believe having the cages directly on top of each other would be fine. However, I'm sure that the use of spacers would technically be safer.
A compromise of sorts is take make the grooves for the cords deeper and wider than necessary. Since your using 3/4" melamine maybe 3/8" x 3/8". If you go that route maybe place the heated area about 3" from the back so the heat does not have far to vent and you're not weakening the floor too much.
Make sense?
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Current snakes:
0.2 Gonyosoma oxycephala - (Silver/Yellow)
3.3 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)
3.3 Gonyosoma janseni - (Black & Tan)