Photoshop :: Resize All Layers In Document To Specific Size?

I'm looking for a way to resize all the layers in my document to a specific size.  I'd like to resize every layer to be exactly 6 inches in height (while keeping proportions constrained).  I can manually transform every layer to do this but I haven't found a way to do this automatically to all layers,  I've tried to do it as an action but it's recording it as a percentage and not a fixed height,  so it doesn't work on the other layers that aren't the exact same size.