Watch the Overview of Triad Positions online guitar lesson by Matthieu Brandt from Guitar Lab: Triads and Hendrixian Double Stops
The third and last position for triads on the middle three strings contains the exact same shapes as the previous two. Keep an eye on where the root of the triad is AND where the tonic of the key is.
Knowing which chord degree you are on, where the root of the triad and which extensions sound good on that particular triad is essential in creating smooth arrangements. All these triad notes also give you the strong notes for your solos.