Looking for stale-bedding / occultation / tarping advice

I'm looking into using the tarping method popularized most recently by Jean-Martin Fortier in The Market Gardener to help with weed pressure in our permanent raised beds, and was hoping to get some practical advice on materials, timing, and effectiveness from someone that's actually tried it. I have a few questions/ideas:

1. Does the material need to be water & air permeable? I would suspect that since the method is meant to encourage weeds to germinate and then die off from lack of light (not lack of water or CO2) it doesn't matter if the chosen tarp material is permeable. And I suppose that if the area was effectively air and water-tight (non-permeable material) you would technically be solarizing the beds and compromising the soil biology/earthworms.

2. JMF recommends using silage tarps, justifying the cost by touting their durability. In looking for cheaper alternatives, someone recommended using rubber roofing membrane (apparently this usually goes into the landfill when buildings are renovated/demolished) cut to manageable size. My immediate red flag had to do with toxins leaching out of the membrane, but I can't find any research to back that up, and in fact it's used in roofing expressly because it does not contaminate the water runoff. Other alternative materials I've seen include polypropylene woven ground cover (aka landscape fabric), and... well... really just that one. Farmtek's fabric remnant section is about the cheapest place I've seen it, but it's a gamble as to what color and weight you get.

3. Any recommendations as to size or tarp? JMF makes his to fit one full bed, which seems to make sense on a small-scale operation. The rolled-up tarps would be more manageable, but you'd spend more time laying out individual tarps.

Any thoughts or advice out there?