Here you can get (for free, no license) scripts for Raspberry Pi hdmi timings .
CRT_Open_Screen.py :
This Python script can open 'on the fly' a hdmi_timings for CRT.
Use it like this (for Amiga uae4arm) :
CRT_Open_Screen.py 1920 282 49.920410 6 4 11 48 192 240 5 15650