I am having trouble with this install. Two quick questions: Is the front of the cover (up against the cab) held in place just by the rails? When I go to close my cover it slides a bit. I am concluding that my rails are not tight enough. The current model only has 4 clips not 6 as shown in most videos. I am having trouble getting them tight enough. Is there a trick to that? They aren't sliding but they are definitely locked tight. Thanks!