I assume you mean that the sides taper from wider at the waist to thinner at the neck end and stay the same width from the waist to the tail block. That is how I build my tenor ukes. I also put a 25 foot arch into the back. This does put a little tension into the back but not enough to cause any problem with the glue joints. Some builders taper the whole way, some don't taper at all, some sand a dome onto the sides to match their domed back. Whatever works for you is fine, but you don't need to worry about the glue joint failing due to the small amount of stress put on it by that taper. Do understand that if you tapered the back the whole way it would not mean a straight line taper to the sides before you bend them.