The Fault Line/Lower West Rim trail has many offshoots that will test your skill level, there are bypasses for the harder obstacles.
The Sand Hollow trails are rated anywhere from a 5-9, most of the difficult obstacles have pass arounds. It is strongly encouraged that your SxS is at least 60″ wide with long travel suspension. 50″ trail version machines will struggle with most of the obstacles.
Lower West Rim/Fault Line is rated from a 4-7.