Just had the PVC tarp done. Pretty happy with it! Has two big air vents at the front that can be velcro'd open / closed and that have mesh in them also.
It rained last night - no water ingress around the accessory mounts up the top.
You don't mate. Apart from the thread holes, PVC is waterproof so a bit pooled on top isn't a problem if the seams are filled with seam sealer. If you aren't parked on dead level ground, it just runs off anyway.