if you could do your modeling with 16 gauge tubes, 0.065", that would make your data more comparable to conventional practice and the other modeling we have done.
I think there are a couple of small changes from the Locost chassis in your model. One is how the inner bottom tubes in the engine bay meet the lower tubes along the transmission. In the Locost they don't line up and with the standard load we were applying ( 1000 lbs. to the coilover mounts ) it was enough to exceed the yield limit of the tubing. It was over 70 KSI of bending where the tubes didn't form one node.
As has been mentioned in the "frame questions"
http://www.locostusa.com/forums/viewtopic.php?f=39&t=18265 thread, I resented the amount of metal going into the transmission / driveshaft tunnel when It could also be placed into the main frame rails around the passengers. In the Car9 modeling I gained a lot of stiffness by making the area under the scuttle well triangulated. Even one part of the upper surface of the car being triangulated is a big contribution. So that requires moving those upper leges around the transmission to the tube across the car under the dash and making a "W" shape.
I found I got excited doing this work when I got to the point of changing a tube at the rear of the car and seeing the stress on a tube at the front of the car double!
Then you have to figure out if that's a good thing or a bad thing. Lots of pondering, but what a playground for an engineer!