Rack system/tub questions

Alright, Im having a friend build me a 4 shelf rack system for 32qt tubs. Im going to put flexwatt in them.

So my questions are:
What size flexwatt should I put on each shelf? IE length, and size.

Also, what kind of material is cheapest, strongest, and appropriate for this rack system? Does it need to be painted?

Do I simply tape the flexwatt directly to the shelf and slide the tub right in on top of it?

When drilling the ventilation holes in the tubs, how many and how far apart?

Will one of the reptile basics large hide boxes fit comfortably into the tubs?

Sorry for all the questions, Thanks!

- Braedan

i use enough to go the width front to back on my rack.

http://i4.photobucket.com/albums/y14...k/100_2231.jpg

My adult tubs have one 11"x12" piece that fits just below the hide boxes. I also use reflexix (sp?) underneath the flexwatt. The baby and juvi tubs have the eight or ten watt per foot flexwatt running the length of the rack towards the back. I've seen it used in different places and I think it's mostl the way you want to do it.