rocker questions

Hi, I’ve spent the last few months researching various books, videos, and of course the swaylock’s archives and I’m ready to start my first board. My original plan was to build a longboard, but I’ve changed my mind and am now planning to shape a thruster (i don’t want a fish) for soft waves up to head high. The longboard will be board number two. Anyways, before I go ahead and order my blank I’ve got a few questions, especially concerning rocker adjustments. I’m 5’9" and weigh 155 lbs. My current thruster is 6’4"x11x18.5x14x2.25, and works great in small, steep, hollow waves but suffers in softer surf. Therefore I’ve decided to go a bit shorter and wider on my new board, in hopes that it will give me a bit more speed through dead sections. I’m planning on ordering a 6’3"R and shaping it into a 6’1"x12.5x20x15x2.5, widepoint centre, rounded squaretail with a long, shallow single concave. I want to keep the rocker as flat as possible for speed, but am worried about the board becoming too stiff and hard to turn. So in order to compensate I would like to have a bit of tail kick to loosen the board up and help it go vertical. So my question is, what rocker adjustments should I make to the natural rocker of a 6’3"R in order to get a low, fast rocker with a bit of tail kick? I don’t want a huge tail rocker because I’m worried that it may slow the board down, I’m just trying to find a good balance between speed and manueverability. Are there any problems with my design that any of you more experienced shapers can identify? Thanks in advance, I appreciate any help that you can offer me.