Perhaps, I should have reordered my first paragraph:
The promise and reason for monocoques was/is equivalent or greater strength over space frames with equal or less weight (why else would a racer go with a different design). Beyond this "promise," it is very hard to make generalizations about one technique vs the other. As in all things, it is in the implementation of a theory that the rubber meets the road. Given your design capablility, Fran, I have no doubt that your monos are stronger than some (maybe many) space frames. Without a doubt, they are stronger than a single plane ladder frame as used in your example. But, your example proves my point: one must compare design/implementation to design/implementation, not classification to classification. That's all I was saying.
That said, there is no doubt that monocoque has a unmistakable coolness associated with it. An inherent provenance that comes with the fact that the most advanced race cars, both metal and composite, have been constructed this way for quite a few years now. This has an allure to a great many people, and I must admit that I am one of them. On the other hand, I don't want the guy with a space frame car to think that he, automatically, has an inferior car: that just isn't necessarily the case.
Scott, 5/16" is the diameter. Body of rivet has closed end that is bonded to mandrel, which is designed to remain in the shank of the rivet. The tunnel is not formed around a three dimensional frame (it's a monocoque design, if you will), so, no my chassis is not a backbone design. But because of its height and the way it ties in, front and back, to the space frame, it acts very much like a backbone design where longitudinal rigidity is concerned. The tunnel, together with the way the sponsons are sheathed, do add to the torsional rigidity of the chassis also.