I would split it so the top and bottom would be full width. The sides would be just the narrow parts between the top and bottom.
Alignment of individual parts of a single design file are very good. There shouldn’t be any gaps.
If you were designing with vector shapes in AI, I think you can draw a line to cut shapes into separate pieces. Do that across the full width at the top and bottom of the opening. Then make the parts of each section a different color so they show as 4 operations in the GFUI.
For raster images, there is this recommendation for large engraves, tiling multiple images to form a single whole.