Tips to resolve lag?

I'm in the UK and trying to play games with someone in China. The lag starts out at about 1 second and seems to increase steadily until the game goes from almost unplayable to completely unbearable. The ingame ping indicator is at 999 basically all the time. We both tried hosting and I turned on port forwarding in my router as recommended elsewhere, doesn't seem to help at all. We can video call each other easily enough so the bandwidth should be sufficient. Does anyone have any other tips for reducing lag? Does using something like hamachi help?

Alternatively, is it possible to change the settings so that the game only shows the locations and states of objects at rest (we don't have to see each other drag stuff around, it's just the final location that matters). Updating counters works fine, it's when objects are moved that the game needs up to a minute to update.

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Cheers