Page 2 Modeling Trog: Torso

Select the profile curve that forms the back (not the ridge reference curve) and then pick the right side, front and left side curves in that order and then hit Enter.

The next thing CSec will ask for is for the first and last point of the cross section line, which will create a cross-section of the profile curves. With the 'Point' osnap on select the upper left point and the point directly to the right of it and continue connecting the points creating CSec curves across the profile curves as shown below and hit Enter after completing the curve.

Note: Where you put the cross sections is important to the result of the loft surface. The basic rule of thumb with the CSec command is that you need to put more cross sections where you need pick up more detail, for instance if you were doing a arm you would want more cross-section's around the elbow.
A different approach would be that we could select the four profile curves and loft them and perhaps use 'Rebuild with 10 control points' option. But a more advisable approach for a tubular object like a torso, arm or leg is to use CSec on the profile curves to get a series of curves running down the torso which can be lofted in a more controlled manner.

Select the new curves generated by CSec and hit 'Rebuild with 8 points.'

With the curves still selected hit PtOn and select all the points that form the corners of the curves from the top view as shown below.

Square up all the curves with Scale2D all at the same time by selecting the approximate center of all the curves as the origin point and with shift pressed pick a point outside the curves as the first reference point and pick and point a little further out than the first reference point or type in 1.14 as the scale factor.

Or watch the scale factor (after picking the origin and first reference point) in the lower left corner of the workspace (just to the right of the X: Y: Z: info and drag until you have a factor of about 1.14. as shown below.

Note: Or you could eyeball it, which is the way I hope you start doing it. Try to go with lines that look right to you and try to get into a creative flow whenever possible.