I just instalked one on my 16' Sylvan. It will never be in that exact perfect position because the boat moves and so does the sun!! Most are way to tall, so when you sit down, the sun comes in under the side and the top becomes useless. One thing you can do to help is add sliding rails on each side. They come in a variety of lengths, I used 24" long so the top can be moved forward and rearward 12" in each direction. The other thing I do is to get as low a top as I can. I am only 5'6" sobwhen I stand up, my top is right on my head, but, I have more shade when sitting down. With the rails, your position is not as critical because you can slide it back and forth to help get the shade you want. This also allows you to slide the top to the stern to stow it out of the way. Hope this helps, I have installed numerous bimini tops, would never install one without the sliding rails, way to many advantages of using them.