Had to use my ladders to access a flat roof today (higher than your normal garage roof) the ground was cobbled, wet and green and i could barely stand on it. Fixed the limpets and up the ladder i went. I tried to make it slip away whilst stood near the base but it wouldn't budge. Very impressive bit of kit.
Don't know if they could slip if i got above second storey level but at the height i was at today they were rock solid.