Hi Noob - so one thing that would probably help with manipulating shapes would be to use fewer curves, right now your current setup is rather dense with cross sections and the more sections you put in the more constrained the shape will be and it becomes easy to have bumps and undulations in the shape.

Another thing that can help is to use the "Loft style = Loose" option which will tend to make a more relaxed surface. With that option the surface will only be guided through the cross sections and not go exactly through them, so your cross sections need to be a little larger than the final shape for that mode. You can also include a point object (draw it in under Draw curve > More > pt) at the front and back to make your loft closed, that works best with Loft style = Loose as well.

For your trimming, one complication is that one of the internal edges of your loft just barely skims right along the same bottom line of your trimming curves. You can still trim with that, but it's possible the Trim command may get confused in the step where it asks you to pick which pieces to discard, you may have to just push "Done" there and then select the faces after that and use delete if you want to get rid of them.

You may possibly want to run the Rebuild command on your loft cross sections before lofting them to make those curves to be just one single smooth curve rather than a segmented curve. Info on Rebuild here: http://moi3d.com/3.0/docs/moi_command_reference10.htm#rebuild


.... After a bit more investigation it looks like there is some bad shaping near the back of the shape where the surface is kind of strained and probably zig-zags back and forth over itself, creating a self-intersection. Self-intersections in a surface will cause problems with intersection and cutting operations so that's probably what is really messing up the Trim in your case here. Here's a screenshot:






Maybe try running the Rebuild command on your cross-sections to eliminate the segmentation in them and make them made up of just one smooth curve segment, that will avoid the compression that is happening currently since one of the segments in the end section is very small I guess.

Hope this helps!

- Michael