Brian,
Yours fit like mine do, sort of centered - but.
I've seen this question asked many times and the only answer I've found was they need to be "centered". However, the answer how far in or out has remained elusive. My own opinion is the tip to muffler weld must be inside the trim ring which would be the furthest out to the rear extension, and for how far in they should be seems to be the rear most part of the tip would be even with the forward edge of the rear bumper. Confused? Look at the weld, and look at the bumper when installed.
(Here, hold my beer.)
Jim