I was going to make the same suggestion as Scrivet. Your fence post pipe is heavier gauge than most tail pipes, and the manual expander may not work well. The hydraulic rigs that the muffler shops have will handle much heavier pipe. I know you did not ask about this part, but in my area the muffler shops will do an exhaust job including labor cheaper than what I can buy the parts at a parts store.
"The Constitution is not an instrument for the government
to restrain the people, it is an instrument for the people to restrain the
government lest it come to dominate our lives and interests." Patrick Henry