14 and 3/4

Just when I thought I was done sanding the pipes, I realized that they wouldn't fit in the 14 3/4" space that they needed to. Even with pipes #16 and #17 on their backs, they were still about an eighth of an inch over where they should be. That meant sanding down the sides of the pipes in order to get them all into a tolerable cumulative width.

Melvyn's comment a few posts back - about me still having all my fingers - turned out to be slightly prophetic as I worked yesterday on sanding down the sides of the pipes with my inverted beltsander contraption, which I've now nicknamed "Ol' Bitey":

For the following reason:

Anyway, armed today with a thick leather glove, I kept sanding until I got within the desired measurement: