Lower body Gluteal Goddess modification?

Hi everyone! I finished the Gorgeous Glutes (lower body) program in March and I absolutely loved it. The reason I chose the Gorgeous Glutes instead of Bootyful Beginnings was because I had my own routine for my upper body days that I wanted to stick to. My schedule was workout A, B, Upper body, A, C, Upper body, rest. Since then, I still have four lower body days, but instead of doing the set workouts from the book, I just choose my own SC exercises to do on those days.

Gorgeous Glutes was very effective for me (I gained two inches on my booty!) and I want to start the Gluteal Goddess program next week, but I'd still like to stay with my own upper body routine, if possible. Does anyone have any suggestions on how to do this? I'd be missing out on the supersets I guess, but are there any other downside to doing only the lower body exercises from the routine?

Thanks! :)