First of all, let me just say that I LOVE BFL. I've been a BFL'er for a very long time. Of course I do "fall off the wagon" every now and then and have to get going again (usually a few months before my February Mexico trip!) and I kick myself for it every time! All I can say about the way the program is designed is that IT WORKS! It has worked for many, many people - people I know. When I had the honor of meeting and then going to dinner with Porter Freeman and his trainer Eric Shreives (a picture of us in in my Picture Trail album link below), I asked Eric that question about my triceps. I told him that I really wanted to firm them up more and should I be doing more excercises for that body part. He said absolutely not. The program works as it is. He says that's all you need to sculpt your muscles.
Now, that being said, since I was a runner for so many years and now a cyclist, my aerobic workouts typically have ranged anywhere from an hour to three hours for the last 20+ years. So for me, I thought it would be best if I made it a point to keep doing more aerobic activity than what Bill recommends because that was what my body was used to and I worried that if I did less I would be going backwards. And as Mexico approaches, I add in more aerobics on my weight only days so that I can proudly wear that bikini. During cycling season I cycle on most of my weight days too. So whatever works for you.
But the bottom line is that BFL will ONLY work if you follow the eating plan. It's simple, but you've got to be honest with yourself on portions, etc. If you do it all like Bill says, it will work. You can get success videos from the website for just a few bucks each (there are two) and the stories are amazing!
Sorry for such a long response. I'm just a little pro-BFL. I hope it helped. I can e-mail Eric or Porter for a specific answer to your question if you would like. Or you could call the 800 number and I bet they would answer it for you.
Susan
"Until one has loved an animal, a part of one's soul remains unawakened." - Anatole France
http://www.picturetrail.com/dogs2birds