If you build it by the plans you should be okay. If you can extend the nose a few inches it may eliminate the need to add additional weight. I had to extend the nose by 5 inches on a glider I built a few years ago but it is worth the effort. I always recommend using plastic hinges and expoxing in place then drilling a hole through each side and expoxing a toothpick through the hole. This means you have attach the control surfaces before covering the plane. But you can cover the hinge points before installing the hinges. I've seen too many planes lost that used CA hinges.

The Slow Poke flies great and will do etremely tight loops. Because it has such a big wing surface you can do slow sharp turns and not worry about it going into a spin. One word of caution, that large wing surface is not made for windy days. So watch out...