[Captain Kwok]

It could also be a double space after some entry you edited or changed, that would cause the remainder of the data to be 'ignored' and perhaps be responsible for a save-breaking error.

Try this:

Take the original data file, copy the armor entries to the end of the file. Adjust their values and change their family number to something no other component has. This should work and the component should be listed at the end of available components when designing a ship.