It probably depends on the tightest bend it has to make. I know a guy who makes pipes but he makes cone pipes using a bunch of cones/rings. Not that easy to do but might be easier than making a 1 or 2 piece pipe. The other thing to consider is how to make the pipe give more HP or a better HP/torque curve. Expansion chambers are generally used on 2 stroke engines and can make a huge difference to the stock pipe(s).