adding weight (as in rocks or logs) on top of the guy lines is a very effective way to secure the tarp in high wind.
when hard wind gusts hit, it will lift the weight (as long as it's not to much weight), allowing forgiveness to the tarp & guy lines.
here i used a grill that someone had left behind to distribute the weight over a larger area & provide a smooth surface between the guy line & the rock.
to much weight can result in a failure of guy line or tarp. this picture is dark but note the torn tarp corner.
large limbs laying across the center tie outs help buffer the wind blasts.