I wanted a pipe tool like the Rhino one so I downloaded your script, pipe.zip. This script works great except that it will not cap a pipe with an outer radius of 0.55 and and inner radius of 0. It works fine with 0.54 and 0.56, just not 0.55. (0.549 and 0.551 work as well) Very strange.

Add to that 0.425 and 0.426.