I found the spec version a bit light bodied and wanted more robust fruitiness, so used 15 Cocchi Americano Rosa, 10ml Dubonnet and added 2.5ml sugar syrup to help bring out the apple, as Avallen is so dry. Could possibly even go to 5ml sugar.
I wonder if “a la roy” is actually “a la roi” i.e. according to the king - with an older, historical spelling? Be curious to know more of the origin of the name here.