Don't try this at home
A recent link sent from Bluegrass on the Tube was to this video (also on YouTube) of a performance of the Gordon Lightfoot song 'Steel rail blues' by the US band Rockin' Acoustic Circus, who are now known as Belfry Fellows.
Neither name suggests a straight bluegrass band; but the only unusual feature in the video is the presence of a carbon-fibre cello.* This led me first to the website of Luis and Clark instruments, and from there to the 'Viola-Matic commercial' which can also be seen on YouTube. Warning: however much you may believe that instruments built with traditional methods and materials are superior, don't use them for the same tasks.
* All instruments of the violin family are available in carbon fibre; Tim Stafford of Blue Highway has played a carbon fibre guitar for some years; New Millenium Acoustic Design have made highly regarded mandolins in carbon fibre; and banjo tone rings are already being made of it. Just a matter of time before the first all-carbon-fibre bluegrass band appears...
Update 30 July: This YouTube video shows the making of a Luis & Clark cello; note that the neck is moulded as a unit with the back and ribs of the instrument.