Hi computerchic and welcome (waves hi to Mark as well!)
It was quoted to me that with fractionated, hearing retention should be (barring risks) within 5-7% of what hearing was at time of treatment (CK). I cannot answer as it pertains to GK.
As Mark noted, my last hearing test, which was 8 mos post treatment, showed my hearing has diminished 10-15db with slight decrease in voice recognition (from 100% to 96%.) My next hearing test is next week, so will update then. I can tell you that I can still hear fine (I was at the bottom of the "normal" range at my last test), use my AN ear as my "phone" ear and otherwise, I claim "selective hearing" when it comes to my spouse
If you are looking to do a form of radio-treatment, there are many interesting threads in the "Radiation" forum and in the "Archives" that people have shared data, experiences, etc, as it pertains to their hearing, balance, etc. Maybe worth a peek.
Hang in there... welcome... and we're here to cheer you on.