[Retros] Fake castling speed record

[Joost de Heer]

Hello,

Does anyone know what the current fastest 'fake castling' record is? I 
can find a Gruber proofgame from Schach-Aktiv 1978 in which the fake 
castling is completed after 6.5 moves.

I found a 5.5 moves proofgame with fake castling yesterday, but it's so 
ugly that it probably isn't worth publishing.

Joost