i'm sold on the full ridgeline, either over or under don't matter.
it makes everything very easy. you can string the ridgeline, while keeping the tarp in a stuff sack skewered to the line at one end. hillbilly snakeskins essentially.
utilize prussiks to set tarp position over the hammock. doing so, you can tie the tarp out, and then stuff it back into the stuff sack hanging on the line. now, you're all set up and staked out, tarp is ready to deploy, but out of view.
i've tried a multitude of setups. i find this to be the most convenient. it also "babies" the tarp by keeping it off rocky / muddy / crudgy ground.
-jeff beck per usual always.