One gearbox with 2 CIMs on each side would, overall, deliver more power to the wheel(s) still in contact with the carpet. However, traction then will come into play.
If you're using #35 chain, it is more forgiving. Allow for chain tensioning as well, and be certain your drive and wheel sprockets are aligned. Some teams use #25 chain, and wheel alignment and chain tensioning are much more critical to minimize potential chain walk off from a hard hit from the side.
