I just had another thought: how necessary or how much strength was the '3rd' tube adding? So I ran another situation:
Long story short, it is similarly strong. The largest deflection does go up from .7mm to 1.9mm (which is still less than the original design 3.1mm), but the weight goes down a full kg (on each side).
This design does put the largest stress on the front bottom corner vs the other designs put the most stress on the rear bottom corner. So if I go with something like this I would consider a large gusset at the front bottom.
