What is the best way to add a different sized page into a chapter

Working on FM 11. My graphic is in the middle of chapter 1. I made another file for the foldout, chapter 1A, and split the existing chapter around the foldout chapter. Now I am trying to get the second part of the chapter, chapter 1B, to continue the paragraph numbering, but it has restarted. If I set the chapter to continue - it increments the chapter number to chapter 2, which I don't want. If I go to the sub-section tab of the numbering properties, the choices to continue from previous chapter are greyed out. What combination of settings do I need. Thank you for being patient with me.

It's still as Error mentions, FM only supports one physical page size per file. Therefore you need to split your file around the 11x17 insert and use the Book file to control the numbering. You may want to consider modifying your content flow so that the oversized inserts always go at the back of a chapter/section or are inserted as an appendix with all over-sized graphics in one location.

Historically, you'd do those pages as a separate component file in the book, then render the whole book to PDF as if for the larger page size. You can set the Chapter-Number to not increment.

I don't know if newer versions of FM have any advanced capabilities with respect to varying page sizes.

As infrequently as I need to do it, inserting the odd-size pages by hand downstream in Acrobat Pro also works.