We were out last week on a trip, whilst in Lakes Entrance, it was expected to storm and pour rain, even though we had seasoned our camper, there was a tiny leak last time we were out (Wilson's Prom) again in massive rain (seems to be something about our camping), we put our tarp out over the camper to ensure there was no issue (we hadn't got a chance to put some seam sealer on).
The way we put the tarp up was (as ours it a hard floor), simply connected the tarp to the rear of the camper (the rear once folder out - whilst closed it was at the front) whilst closed, and as the camper opened up, it dragged the tarp over the roof. It was very easy, and all we had to do was put on some ropes and all was good - didn't move at all.
The rain was pretty noisy on the tarp (as opposed to the canvas).
We want to get to the point that we don't need a tarp, at the moment we would only consider if we were expecting very heavy rain.
Hope this helps.