That's awesome! The symbols for shipwrecks and Caliphate cities rock, and the option to add hex numbers makes it eminently gameable.
Hex map distances are usually 6 miles from side to side. If the hexes are oriented so the "flat" side is facing north, then you're right that moving 20 hexes due east carries you less far than if you move 20 hexes due north. (You can see this in Hexographer by setting up a 20 x 20 map, which is visibly not square). The distortion is less than in 4E, where 1 diagonal = 1 lateral movement means you can go a lot farther in some directions than others, and I suspect roughly equal to in 3E, where 1.5 diagonal = 1 lateral.
I just got the 1E Wilderness Survival Guide from PaperbackSwap, and just about the only thing in there that looks useful is a brief discussion of hexes. I know it has a picture of how to collapse smaller hexes into a bigger hex depending on how they're oriented (the secret is that the orientation always changes from little to big), and maybe the answer to this question is in there too.
I've certainly spent a lot of time worrying about details like this, and have to keep asking myself "what difference will this make to the game?" At first glance I don't see why it wouldn't be better all around to say that to get from east to west, you count out 20 squares in kind of a zigzag, so 20 x 6 means you travel 120 miles. There might well be reasons not to do it that way - one of the cool things about trying to faithfully capture reality is that it sometimes has unexpected effects on gameplay. But certainly the Wilderness Survival Guide exemplifies a chasing after quantified "realism" without ever seeming to think about how you would use it in play, or why you'd want to.
