

Drastically reduce filesize of PSDs by adding white layer on top and zipping - niyazpk
http://idletogether.com/how-to-reduce-your-psd-files-size-using-photoshop/

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ComputerGuru
Or just disable thumbnails when saving......

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noonespecial
Don't forget to turn of "compatibility mode" as well. This saves a raster
image of the entire (visible) document as well as all of the layers. Adding
the white layer on top would make the compatibility image nothing but a plain
white image. Just turning it off would be better.

