How about d500 or d600. Because that's when the Nightmares would've got icon in reality.
AH Lag favours the chaser. Because you see his old position, you see an aircraft rendered slightly behind where he is. Because he sees your old position, he sees an aircraft rendered slightly behind where you presently are. So the mossie might've seen an icon at d800, but by then the LW pilot was seeing d600.
ie, the nightmares only got icon when the LW already had a firing solution, so for all intents and purposes the icons were effectively off.