Craftmanship quality can be captured in a couple of ways:
-builder reputation
-fuselage/wing finish----generally speaking, if the builder took the time to give the aircraft a very smooth finish, he probably took the care and effort to build it right (the exception to this would be the builder who covered up all his sins with a smooth finish)
-documentation. There are many builders who have documented their effort on the internet. They took pictures of everything---you can see all the layups and see what kind of quality work actually went in it. Some people did not document on the internet----but they do have the photographic evidence
-aircraft hours. An aircraft with lots of hours may be evidence of a nice, safe, flying airplane