Yeah - I think the idea of drilling holes in the wood is the best option.
Not really fussed about metal or timber - just hadn't really considered metal.
We have fridge on left, other stuff at the side of it, and the gazebo and tent go across the top of the whole lot, with blankets & pillows etc by the windows to prevent damage/movement. Would be keen to heard more about the guards
The main reason for building this is so that when the car is packed, we can still get the fridge open - so it would need to have a sturdy top that will take the weight. I like the idea of covering it in carpet, both to look tidy, and also the other stuff slides against it quite nicely (nothing to get caught on).