CrazyBike2 had no cetner triangulation for quite a long time (removed for weight and for cargo space enlargment), and made it easier to stow cargo in the center, like dog food bags, battery boxes, etc. But eventually teh twisting and flexing cracked thru the toptube, and during a laydown/slide during an emergency stop last year, it finished that off. If it weren't for the construction methods and design of the seat/etc, I would not have been able to ride it home...but I made it the rest of teh trip like that.
It now has triangulation bars there, though.
It's replacement, in progress, will have one solid bar on one side and one removable on the other, so I can still use it for battery or cargo but still be stronger/less twisty. Optionally it might just get side covers that bolt to the "four corners" instead, doing the same job.