If your plant has shot up in growth and is approaching the top of the unit, there are a couple things you can do.
1. Push your coco pod through the lid. This will give you several extra inches of space as you drop the plant into the reservoir. By now it's big enough and will be just fine with the all of the roots in the reservoir.
2. Use support racks to keep the branches off to the sides of the unit, out of direct contact with the LED light.
3. Learn the horticultural technique called 'supercropping'. Check out THIS article.
5. Check out THIS article on lollipopping. It will help focus your plant's energy into the buds.