Although I'm not CT, usually the best advice always comes in the form of keeping things as simple as possible. If you train in the mornings, try using Power Drive afterwards (one-two scoops). If you get tired around 3 in the afternoon, you can consider either of the two options:
(1) Eat a meal higher in fat and protein between 12:45 and 1:30 p.m. (this has actually been associated with higher level of mental stamina, which may reduce drowsy feeling)
(2) Have one scoop of supplemental protein with one or two servings of Power Drive around 1:30 or 2 p.m. However, I believe it's not recommended to use Power Drive too late in the day (perhaps no later than 4 or 5 p.m.).
In sum, adjust the Power Drive dosage/timing to fit your needs (find your "sweet spot," as Chris Shugart mentioned). If all else fails, simply take a nap if possible, or get more sleep at night