Hi Andy, can you post the rail and profile curves you're using to do the sweep, and also the main body surface that they're on?

A couple of possibilities might be to put in a scaling rail to guide the shaping instead of using "pointy ends", or maybe draw in some curves from the side view of your body, use Construct > Curve > Project to project them onto it and then use 2 rail sweep instead of one-rail sweep.

- Michael