Hi Dan - in order to do a proper job of re-orienting any object in a controlled way, it is necessary to have a base reference plane, in addition to a target plane.

For a planar curve it could be possible to use the plane that the curve is in, but that will not work so easily for something like a solid that is made up of many planar pieces rather than just one.

So my general plan for that is that I want to add an "Orient" transform tool that will handle this kind of task, I don't think I can make copy/paste do it without forcing you to do extra steps to specify a source plane at the time that you did the copy, which would be weird for the cases where you did not intend to paste to a different orientation.

I'm not quite sure when I will be able to get to the orient command though.

In the meantime, from reading your description re: sweep - the first thing is if you want your shapes to be distributed uniformly through the sweep path, then you can use the "auto-place" mode of the sweep which handles that for you. To use auto-place mode, you put all the profiles flat on the construction plane a little distance away from the rail curve (outside of its bounding box). That will make MoI automatically distribute and rotate your curves to be perpendicular to the curve tangent, see here for some examples:
http://moi3d.com/1.0/docs/moi_command_reference7.htm#sweep


Otherwise, if you do need to paste copies of a curve oriented along a curve, try using Transform/Array/Curve for that. You can either make a large number of copies like say 200 of them and then select the ones you want to keep and do a Select/Invert and delete the other ones, or also with the v2 beta it is possible to drag a reference point on the curve for a distance of where to place a copy at a specific distance, like this:



That may be an easier way for you to get the job done currently.

- Michael