2 weeks follow up.
After playing around I realized some things.
The main conclusion is that, if you use in situ audiogram for your hearing aid, you most likely will be fine without real ear confirmation. It only works with IN SITU AUDIOGRAM for first fit and your manufacturer fitting, not NAL-2. You cannot use your audiologist audiogram for first fit.
Read on for details.
Most Importantly and #1. I used my audiologist audiogram for the real ear measurements. When I used it for first fit, there was often >10 db difference between frequencies over 4 K with all hearing aids. When I used in situ audiograms with each individual hearing aid first fit, only one differed from my audiologist audiogram real ear measurement by more than 3 db. 2 were perfect fits between 4-8K. The only one that still failed >10 db short in the high frequencies was the Signia Silk. I had to go through and use the frequency shaping to match the higher frequencies.
Second. Don’t play around with compression much. I used compression to match perfectly the 50,65, and 80 db curves and everything sounded compressed and vomited out. It was perfectly understandable but unpleasant. Using the gain only to match each level cannot achieve 3 perfect curves, but if you match the 65 db perfectly everything else sounds great. If you have more of a hard time with soft sounds you could base it on the 50 db curve, or compromise, but over compressing sounds absolutely terrible.
In summary, you probably can use your in situ audiogram without real ear measurements with Signia active pro, Signia pure charge and go, Phonak Audeo paradise, and I assume most other aids. If you have Signia Silks, your first fit is probably 10 db low, at least, above 4 k.
Edited: I also use speech mapping and the speech sounds for REM as it’s supposed to be more accurate than just using the default noise settings. However it wasn’t a huge difference.