Many thanks for the info! I think that each of the small squares in the large map equalling approx. 10 miles should be about right then, if I understand you correctly. I like to think in terms of kilometres, so I may change it somewhat (If I go with a smaller size, 1 square equalling 10 kilometres should give a size between the two options you mentioned).
I like using metal miniatures, but I also bought RPGs with small cardboard cutout-minis back in the day. Actually the two first RPG games I ever bought in the 80s both had cardboard cutouts (the Swedish "Drakar och Demoner" and MERP). I would love trying it again. Let us know if you make the PDF.