[chirp_users] How to convert from 800-2820 and back?

Please excuse the ignorance. Apparently I was absent the day that we went over this.

What is the correct (or succesful) procedure for converting a file from an 800 icf file to a 2820 icf file?

I can import into Chirp and save as a Chirp or img file. Is there no way to save as an ICF file that the cs-d800 or cs-2820 software can read other than to load directly into the radio with Chirp then read it back out with the icom software?