Hi Lordfox, well it depends a lot on the particular stuff that is making up the 189MB. If it's all little tightly curved things that will take a lot more memory for the display.

One thing that would help is to reduce the display mesh density. By default MoI makes a fairly dense display mesh which makes surfaces look nice and smooth but which can also slow things down on heavier models.

Try going to Options > View > "Meshing parameters" (at the top), and then set "Mesh angle" to 25 degrees and uncheck "Add detail to inflections".

That will make for a somewhat coarser looking shaded surface display but it will significantly reduce the amount of triangles that are being processed for the display and will probably speed things up.

If that doesn't help then I'd recommend splitting your file up into a few separate chunks and work on one of those at a time instead of all at once.

- Michael