Next stop was Castle Lake. The coordinates for the multiple sites is N 41.24385, W 122.38410 I wrote a review of it on the iOverlander app. It is called before Castle Lake. The view of Mt. Shasta was spectacular there as well.
I checked out the trailhead for Mt. Shasta which was reported close to town with lots of sites. I didn't find that to be true. The parking lot was fairly small and it wasnt that close to town.
I checked out the Mt. Shasta Ski Area and found a pretty nice free camping area. Coordinates are N 41.31947, W 122.20482 I also wrote reviews for this on the iOverlander app. Large rigs can use this site as well.
All in all I enjoyed using the iOverlander app for sites that get cell phone coverage. Others are on it but are harder to find if you don't have a wifi booster or an actual physical map.