Hello!
If anyone is interested i ported the new xBR Level2 shader to WinUAE and added a simplified Accuracy feature (which exists as a 2 pass shader in RA) in single pass. The shader works with hires/double line mode and looks surprisingly well with bilinear enabled in Extra settings (some kind of magic lol
).
This makes it somewhat slower but it's a nice feature (makes spiked artifacts go away).