[11douglash]

We've run into much the same problem over the years, except not with weight, but with delivery time.

Taking a quick look at your design, it does look very bloody strong, which is good, and heavy. One thing that my team is looking very long and hard at is building a chassis out of 1/4 inch Al plate that has been machined down. A preliminary image is posted immediately below... But what we plan to do is cut lightening groves in it--- projections put it at ~20 lbs, and it incorporates our Electronics, Gearboxes, and bumpers nicely:

As you can see, it's just 1/4 inch plate on the sides, front, back, and top. Sides hold together the actual Drive Train mechanisms and two internal bars that support the Kit Metal in the middle, the top allows for the side bumpers to be mounted, and the back and front plates allow for the front and back bumpers.