I found my answer.
The extents of the paper space layout preview seems to be set by the layout's limits rather than detecting the extents of the geometry in the layout. This is different from the model space preview which is defined by whatever state you left the drawing in last. You can establish the limits by typing LIMITS at the command line. You can also set the limits by having a pagesetup, that defines your paper size, set current in the layout.
In my case, the limits in affected paper space layouts were usually set to 11x9. Making sure the pagesetup, which defined a paper size of 34x22, was set as current in the layout resolved the issue.
As simple as it sounds, I don't know why it took me so long to check this setting. Oh well.
Thanks for the input.