Hello Matt,
The startup.exe that you create in a module that has 6.1.3 firmware will run on a module with 6.1.1 firmware and vice versa, however this is specific to these two versions. This is not true with other versions though. A LV RT 7.1 app needs the LV RT image 7.1, 7.0 needs 7.0 etc. Hope this helps.
Ayman K