Same here on my '15 Outback. It's not bad at all, even direct sunlight I discovered that it's not that bad (it's my wife's car so I don't drive it much).
Well I got the unit updated to NU9020 today, thanks for the files! Worked like a charm and even did it without the battery charger/keeper. Second file even took on the first attempt.
Okay, I have the files now, but do I really have to connect a battery charger? Someone must have surely tried this without one. I know I should have one anyway though...