I'm building a lean-to on the back of my shop. Shop is an 8/12 pitch but has gutters, so no rainwater from the shop will feed onto the lean-to. I would like to keep the "low" end up as much as possible for head clearance. I will be using metal for the roofing on the lean-to. What do you think is the most shallow pitch I should use. In order to keep the "low" end up, it's probably going to need to be 2/12. Is this too shallow?