The structural integrity of your walls, doors and house foundation depends very much on how you install the rain gutters. To properly protect the house you need to have a good working guttering system that is clean and performs well.
The problem with the slant that you need to look after when installing gutters is that if it’s not measured correctly you will have standing water on top of the gutter.
You have to make sure that you attach the gutters securely to the support so that you have the proper angle that allows the water to flow normally through the gutters.
Basically all you need to look after is that the gutter is installed at an angle that allows water to flow properly. You can check this by pouring water inside the gutter while installing it. Be careful not to angle the gutters to much that it is obvious from the outside.