ah yes now I see my flaw, thank you for pointing that out!
actually there will only be a total of 18'
When I did my math is multiplied my total amount by 2 twice
each shelf is 18" which is only 9' per rack.
I should be safe with 18' between 2 probes and 1 thermostat

If I choose the 4" flexwatt, how should I change the wiring to accommodate for 2 rows of flexwatt per shelf?
I am planning on having each shelf on their own wire, being connected to a power bar. The power bar would be connected to the thermostat.
This way if I am not using a shelf I can just unplug it. (unless my probe is on it, haha)

I have seen the VE-300 x2 pretty often in Canada, I can buy one easily at my pet store, so it looks like I will be going with this.

As for PVCx I love the look of it and I like the comfort of how safe it is to use with my Balls, however I don't know how to work with it, or even where to get it from.. Having a look at the home depot site, I can't find it in their store but they might have it on location
I'll be looking up some how-to video's for working with PVCx, and looking for somewhere to buy it too

Thanks