I used your suggestion, and it worked fine.
I tried experimenting with Rail Sweep and got some surprises. I tried rotating the profile without success. I tried redrawing the profile at right angles, also without success. Then I tried demonstrating the problem to my wife, and it worked fine. I have no idea why - I even tried using different CSs, but couldn't predict what the effect would be at any time. It is uncontrollable.
It seems to me that Rail Sweep is pretty unusable.
Rail Sweep works nicely when you know its secrets.
1) Place a Point object in or near the profile. You'll see why in step 4, below.
2) Activate the Rail Sweep tool and enable "Use compound profile."
3) The prompt at the lower left of your screen will say, "Select an entity to sweep." Click on the profile, which will turn magenta in color.
4) The prompt will instruct you to "Specify the base point of extrusion." Click the Point object. This is the point that will follow the path, and the rest of the profile will tag along, maintaining its relationship with the Point.
5) You'll be told to "Select an entity for the sweep path." Be sure "Use compound path" is enabled and then click on the path. A tentative Sweep is created, but it's not finished quite yet. You'll probably be asked to "Add an entity for the sweep path." In almost all cases there won't be another path candidate to "add," so go ahead and click the Finish flag on the Inspector Bar.
You can edit the profile, or the location of the Point object, or the path -- or any combination of these -- and the Sweep will update itself accordingly. If the orientation of the Sweep cross section is wrong, go to 2D Select mode
; select the profile; and rotate it. You can also edit the size and or shape of the profile, in the 2D Select mode
, and the Sweep will update. Editing the Point or the path can be done in either 2D or 3D Select mode.