[Garret]

I figured out a way in Solidworks that reduces it from a tedious process to a single feature and 2 mirrors (really speeds it up because it eliminates the patterns and associated lag). To do this I draw out the belly pan in 3 steps. Step 1 uses extrude thin, step 2 and 3 use mirrors about the front and right planes.

If I were to do this in Inventor I would do a similar process but instead of using extrude thin (drawing just lines) I would actually draw out the first shape.

In all this process takes the hours long drawing and turns it into about 10-20 minutes. At least for me this has almost no lag, this is likely because the process reduces the number of relations (what slows the model down when patterning).