So apparently it's only me

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All my SH4 installs have the 4gb patch, and no, it's not a laptop. My graphic card is not state-of-the-art, but it's a decent one and has run SH4 for the last 2 years without a problem. It renders 70-ship convoys fine, or the polygon intensive WoWs ships without a hitch.
The drop in framerate happens exclusively when looking at the sub pens. Does anyone know where are they stored?