Hi-
I have done this with the GS series and found that doing the chest, tri, bi, and legs as one bodypart per day was enough to see gains.
However, on back and shoulder days, I would add extra exercises.
If I wanted to do Cathe workouts, I do either the bodypart segments from the CTX series, or Muscle Max.
I did this based on my bodytype... My back is extremely strong and it takes alot of work to fatigue it. I did not feel that the back work from GS did that, but that is probably just me.
For shoulders, my shoulders ( esp side delts) are kind of weeny. So, I am always working those extra hard, and again didn't feel like I was hitting them as thoroughly as I'd like w/ GS. I do switch up for this one, too, using the shoulder workouts from MM, CTX, or ME.
The other workouts were fine. I think the chest and tri workout is absolutely killer especially if you are lifting as much as you can safely handle.
Take care, Lynn M.