Uncle Scrmbl,
If you like I can email you my check 6 files. I have them in German, English (British accent), English (American accent), Japanese and Finnish.
Just drop them in the folder of the appropriate aircraft in the Sounds folder, rename the file to check6.wav and voila, you'll get check 6's in the appropriate language for that aircraft.
You may have to create the folders if they aren't there (you're using Mitsu's sound pack, so I assume they are.
For example, I put the Finnish check6.wav in the 109g2 folder because that aircraft is in Finnish colors.
If you, or anybody else, want them, send an email to aahola@pacbell.net