Review
A distance being as short as 4 miles means that many potential routes are simple and easy methods of hitting the necessary distance. The Add On Loop serves this exact purpose quite well.
With routes that consist of merely one loop outside of the main trails, there is little that can be said about them that does not also apply directly to the one loop that is being primarily run. That being said, doing the Add On Loop does have more effect on the overall route than most other loops since you get off the main trails sooner and only do the section from 1 mile to 1.3 once as it is part of the Add-On loop.
The neat thing about the Add-On loop is that you have multiple times throughout the run to decide if you want to turn onto it or not. If you know for a fact that you want to do the loop before the 1-mile mark, then you have the option of turning immediately onto the trail and taking the main trail back. Or, if you suddenly decide that this is your preferred way of doing 4 miles before the 2-mile mark on the main trail, turning onto the add-on at the triangle is a very solid option as well.
As for the actual trails, they are of solid quality. All of these trails are a part of official horse trails, and they are all wide and well maintained, a feat that few other routes obtain.
The add-on is a very solid method of doing 4 miles. If not for people's tendency to seek simplicity and just do an out and back for 4 miles, the singular add-on would be a much more frequently trodden route.
Rating: Out of 10