If you're looking to gain 8in in 8 months, it's like 17in in 17 days craziness. Yeah, not happening. But if you're already at 7in and pushing hard to get the remaining 1in, that can be achieved. But that will push your tissues into a fast gain and hard plateau situation. I suggest aiming low, at 0.5in gain at an 8-month interval. What extra you gain will be considered a bonus. For me, I only have low expectations and become happier as I gain more. If I'm desperate, there are other means. Since we are altering our bodies for permanent changes, it's best to approach the process slowly and steadily, not fast and furious.