What are the fastest horizontal checkmates for both castlings? Horizontal: wherein the rook attacks down a rank.

I wish to know the fastest possible castling checkmates, for both queenside and kingside, that are a horizontal one

See my question about vertical castling here.
I know this thread is old, but here is my improvement to kingside castling-8.0 moves. Black even has to do one useless waiting move (Ng4).
[FEN &quot;&quot;]
1. e3 e5 2. Ke2 c5 3. Kd3 Bd6 4. Ke4 Nh6 5. Kd5 Ng4 6. Kxd6 Qf6+ 7. Kc7 Qb6+ 8. Kxc8 O-O#

Queenside castling can be proven to be impossible in 8.0.