At a Wellfleet gallery on Cape Cod I remember seeing what I believe were 6x7 centimeter...not inches...contact prints mounted in what may have been 11x14 inch or larger mats. They were apparently selling at least well enough to take up very valuable seasonal wall space this gallery had given over to them. I recall thinking that the prices were pretty high for what they were too (but that's kinda the norm in summer season tourist oriented gallerys anyway.). So...offer them and see what happens. Maybe a big mat will help your stuff as much as it did the work I saw. Or consider it, at least, as an option.