SilverToy - You are a truly a blessed person to have actually lived in a FLW building with original furnishings, but you must have a far straighter back than I. That high-back I tried was too vertical to accomodate my curved spine. I might be able to handle it for a formal occasion, where one is not likely to lean against the chair back, which is undoubtedly what FLW was thinking anyway. But, as I said, the furniture from Usonians seems quite comfy to me, which makes sense given the more relaxed design philosophy of those structures.
And I would never expect any chair design to be perfect for all people, although I do think our new Morris chair ought to satisfy many guests. We are in the midst of renovating an adobe-walled 1910 craftsman bungalow (see my feeble web page about it at
http://www.wesandcarol.com/HouseBeforeAfter.htm). We've seen the Wright repro furniture in the back of American Bungalow, but I don't think it would work well in a house with so many mission elements as this one. I've only ever seen one origami chair repro, but the builder gave no indication he was authorized by the foundation. I'm intrigued so much by that particular chair because it's supposedly made from a single sheet of plywood.
As to the body height issue, the fellowship members we met at both Taliesins seemed to have differing opinions on the degree to which Wright suffered from "short guy syndrome." I think some may be tempted to seize upon that idea because Wright was one of the few architects who so agressively modulated vertical space. For example, he often built residential entry portals with very low ceilings to lead visitors into the grander living areas inside (see another of my feeble web pages at
http://www.wesandcarol.com/cedar_rock.htm for an example). That kind of thinking is unusual in the US, but standard practice in Japan and elsewhere. So maybe people walk into one of Wright's low entry halls, and just assume, incorrectly, that it was built for or by short people.
Condolumium - I think it would be too harsh to say Wright didn't care about engineering. More that he considered architectural design to be his primary foucs. He definitely created some buildings that developed problems, but remember that his Imperial Hotel in Tokyo was one of the few structures that survived the enormous earthquake of 1923, sparking a lot of international research into quakeproofing. Later in life, an MIT-trained engineer by the name of Wes Peters did a lot of the actual calculations for Wright. The two of them were real pioneers with materials and extreme design, so we should expect some of their experiments to be more problematic than ordinary construction.
Come to think of it, the conventional 1992 townhouse in VA that we just sold was starting to develop roof and window problems itself, but I doubt anyone will be interested in living in it 50 years from now, much less restoring it.