What is the most suitable trayback setup to compliment a camper trailer

I have a A139 cub campomatic that I have inherited. It is in great nick and has already done a couple of trips to Tassie, Mudgee and coastal weekends.

I have a twin-cab (PE courier) with an alloy tray. The tray is a good size and has suited me well. The courier is not a work vehicle so is used only for runs to the dump and weekend stuff.

When camping we would put clothes in the camper and everything else in boxes (esky, cooking gear, bikes, chairs, tables etc) on the tray.

Now there is three of us I am planning to put a canopy over the tray- initially to keep extra stuff like the pram dry, and now there is sooo much extra stuff I need to keep lots dry.

My plan was to go with a hard roof and canvas sides. But with a alloy tray I think that a canvas/PVC allover canopy would be best.

So

Q1 Canvas or PVC?

Q2 Windows- useful or useless? (I don't need a window to remember what I put in there and where it is)

Q3 Velcro anywhere?

Q4 Weakpoints and wearpoints- where do I need extras?

Q5 How high? Cabin roof height- I was planning to be just below the roof rack height so the boards can fit on.

Q6 How many flaps - standard (3) or do I split a side to have 2 flaps on the passenger side (I was thinking of a smaller access flap to get to the esky and fridge.

Other points I should consider?

Thanks

Scott