Pro,

If you don't mind an unsolicited comment . . .

It's been a long time since statics class in E-school, but here's what I see.

I agree with what Tech said, but I would leave both of the short, green vertical braces in place. As the chassis flexes upward, you'l get compression in that top tube. If you think about a long stick in compression, it will try to bow out in the middle. Those uprights will be in tension and fight that tendency. I don't see any bending moments to worry about.

I'd also think about an "X" behind the rear axle.