Hi Pat, in my other life I am a framer, and the method of matting depends on the photographer in question. I would mat equally with the edges showing, to mats covering the photo itself, a matter of personal choice.
For my personal work, I usually mat to cover the edges of the print, except when the print is from 35mm, when I print the black borders and allow them to show. I know this is considered passe these days, but I still like it so I don't care.
Some photographers like the black core board for their mats, particularly for high key prints, others like double white mats etc. etc. So you can see that it very much a personal preference, so if you like some of the paper white showing, go for it.
Looks like you are shooting 5x4, if so, printing the edges of the negative can look very effective, and shows that you are not using digital. Mind you, I saw some publicity shots the other day, printed like proofs with the sprocket holes and film ID all included, nice B&W's, but the film was Fuji RDP.....guess they grabbed the wrong program!