This is how we used to do it when guerilla growing.
Doesnt work very well if your RH is too high, which is very well can be in my area, so you'd have to do some weather research for harvest time, but its a way to keep the rains off, and putting it in a hidden spot but one that has a light gust of wind to roll through the tarpend to end or underneath from 'left' to 'right'