Hi Mike, thanks for sending me an example image through e-mail - I wanted to post it here also in case any others had some feedback for these kinds of shapes:




These should be pretty straightforward to do in MoI - it looks like one process you could use for the construction would be to draw a curve outline and then extrude it into a solid using the Construct > Extrude command.

That would look something like this - create a curve in the Front view something like this:



In the 3D view it would look like this:



Select that curve and run Construct > Extrude to make it into a solid:



You can now cut this solid with some other curves to make some more details, for example draw a curve in the Top view like this:



Then select the solid and use the Construct > Boolean > Difference command to cut the solid with that curve, dividing it into pieces like this:



Delete the piece that you don't want and you'll have this final result:




But probably before trying this, I would recommend going through the video tutorials here:
http://moi3d.com/2.0/docs/tutorials.htm

They're not too long and they go step by step through the process of drawing curves and constructing a few different objects, they'll give you a good general overview of how things work. After you watch those the process for the above model will be easier to follow along.

Hope this helps!

- Michael