I guess I never answered your real question-lol. If you plan on incorporating excellent peri-workout nutrition (specifically one of the ANACONDA Protocols), then I would suggest only doing the leg phase as part of the rest of the I,BB (in the exact order the program was layed out).
Otherwise, you would probably be better off just doing a leg spec. phase. So you have two options--depending on whether you can get in the gym once or twice daily.
(1) If you can only get into the gym once a day: make sure you include some leg exercise(s) into your workout
(2) If you can get into the gym twice a day (30 min. in the morning, 40-50 min. in the afternoon or evening): pick a squat or deadlift variation (it doesn't seem like you're a long limbed individual, so stick to the basic bilateral movements). Use Christian Thibaudeau's max force training method with perfect rep technique (ramping every set up to your max force set) for that one exercise in the morning. In the afternoon or evening, just resume with your regular workout. Learning and executing autoregulation is the best way to reach your goal ASAP because it allows you to make sustainable gains.