InfoPath Dev

I have a library which currently uses an InfoPath form for data entry and editing. I also have a new FormsViewer form for that same library, which I can use to create new entries. Currently, clicking on an entry's title will open the IP form for that record, and I can have that click use the FV w/ the proper Extensions configuration. I do not want to change that behavior (yet), but would like to open existing records w/ the FV form instead. Is this (hopefully) possible, and if so, how?

It looks like you can just take the URL for creating a new entry & add a document parameter with the path to the entry to be opened.

Yes, that's correct - good job figuring that out. That lets you test with your existing data without turning FV Extensions on for the list or library before you are ready.