What to put in all those blank spaces

What actually belongs in a Scott International or Minkus Global is not as easy as it seems and in the end comes down to personal choice--after all, this is supposed to be fun :) Obviously, the stamps that correspond to the image or catalog number form the core of the collection although even here there may be multiple options due to color, perforation, etc. But there are also numerous blank spaces for, as Scott terms it, "such rare stamps as may be acquired." The most liberal view would be that as long as stamps are from the appropriate country and within the chronological range, they are legitimate candidates for empty spaces. I prefer a more conservative approach: stamps in blank spaces should be non-depicted issues from the same set or a set with the same design type (but that might have a different perforation, watermark, overprint, etc.).

Some collectors will put closely related stamps underneath one another in the same space--for example, same design but different color. I'm not certain what I think about this although I don't mind putting one or two duplicates underneath so that I can quickly find these for trading.

The final mounting decision is whether to "color outside the lines"--i.e., mount non-depicted stamps anywhere on the page. I'm also conflicted about this as there are undepicted stamps that I hate not to include. But, at some point, I suspect that the look of the page will suffer, not to mention the weight the extra stamps add and increasing the possibility of stamps on adjacent pages catching on one another if you don't use interleaving. An alternative would be use any blank pages for the country if available or to add blank pages although this would separate issues chronologically from their depicted counterpoints.