I would be sceptical of using a rear disc adapter on a carbon frame that was not designed for discs.
the rear disc brake puts different forces in different places on the rear triangle. When we spec’d our Calfee Dragonfly so it could use either a caliper or disc on the rear, Calfee added a brace on the rear triangle to deal with the twisting forces resulting from the disc.
Im pretty sure if you wanted to add a disc to the rear, a carbon repair outfit could modify the rear triangle for a disc mount as well as reinforce the rear triangle
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.