Elements and Focused Flexibility can work together very well! :) It's a good combination, and one that we recommend to many people who want to improve specific areas of flexibility, while also building strength and motor control in Elements.
When combing the two programs, we recommend selecting 4-7 stretches in Focused Flexibility and adding them to the end of your Elements training sessions. You can use these as part of your cool down. You can also practice your Focused Flexibility stretches on your off days, as part of your active recovery.