Worth, I have the Presto 23-quart canner and at the advice of a number of posters on the GW Harvest forum use it at as weighted-gauge plus dial gauge canner through the addition of a pressure regulator that has rings for 5, 10, and 15 psi.
Mine looks like this (but it cost considerably less--look around a bit):
http://www.amazon.ca/Presto-Pressure...JJT84YF082VMCD