Digital BW, The Print

This may be a bit silly, but how much difference in size should there be before 
resharpening an image is needed.

For example. I have some pictures that are 7.5x7.5 at 355dpi and I want to make 
them a bit smaller to 7x7 at 378dpi (no resampling in PS).

The 7.5x7.5 picture is sharpened just as I would like it to be... would I really need to 
resharpen when making a small change down to 7x7?

Thanks,
Jeff