[pfreivald]

Trim weight everywhere you can -- that looks like twice the chassis than is needed.

...and if you don't own a reliable, calibrated scale, buy one pronto. That way, as you modify and tweak from your original designs (which already have estimated weights, right?), you can re-weigh and re-estimate what final parts will be.

We've never been stuck having to drill lightening holes, but then, I'm awfully paranoid about it!