Primary Photo Size

This is a minor issue, but is there a recommended pixel size/photo size for primary photos to keep them consistent? (i.e. some pictures fill the photo box perfectly while others have a vertical bar on either size of the photo box thus not filling the box completely.) RM9

I think / suspect the problem you are describing has more to do with aspect ratio vs size.
I do not recall it is or if its even the documentation. So a 1000p (tall) by 500 (wide) is the same as 500p x 250 as far has the blank space in the thumbnail. Not sure if some know the optimum ratio 4x3 8x5, 6x4 etc