Heh yeah I had that thought regarding size as I went to sleep. I think I will make them just short of the edge, maybe 90-95% of the hex tile width.
And yeah, I was testing a few things with the Right Mouse Button to line trace, call an event on the volume hit, destroy the volume, update arrays to place an Arctic on that tile, regenerate the tile map(with the update), and then replace the volume with the Arctic volume. It works! Except my new arctic volume wasn’t generating 90% of the time, but the tile map swapped so quickly that I couldn’t even notice that anything besides the tile hit had changed. The tile just changes to an Arctic tile as if that is all I was doing. Pretty sweet. It seems the 2 map idea isn’t needed for the smallest of maps on a fairly fast computer, but I will keep it in mind when I test out the largest of maps on slow computers. 
Not sure what is going on with the volume yet, but for some reason my editor crashes every time I try and open the project… -_- Error: 9c26e3bf5ceff148b933522aff1de581
It might have something to do with the question I posted to answerhub: Why won't my 3 separate Blueprints compile? - Audio - Epic Developer Community Forums