[JesseK]

Hmm, 971's bellypan extends to the outer rails. They also have plates on the top of the rails for added strength. Have you considered doing this with your design, at least in the middle of the rails?

I'm no ME, but the proximity of the 4 rivets without any other support raises an eyebrow. The likelyhood of the sheet metal shearing or holes elongating (making the drive not square) seems pretty high.