Like you we have also used ropes and all kinds of rigged up things around trees etc.
We now tend to used a 5 mt plastic wrapped cable, similar to what GG is now selling.
But we usually tie them to either the cruiser or camper, we have tried all kinds of pegs and stakes, but 2 very friendly labs have been able to pull everything we have tried out of the ground.
Will be interested to see what other have tried and had success with also.
Matt