So 5 ft squares = 1,5 m square = 1 square. Sounds good to me!
You could use the scale that Savage Worlds uses too: 1 square = 2m x 2m
In short, you are playing with bigger squares, but that doesn't ruin anything; however it's really fast and easy to have measurements: 1 human miniature occupy 1 square, and that is also its height; finally, if you have a distance (ie. 50 meters, it's really easy to obtain the distance-in-squares... 50 / 2 = 25 squares). I love squares in Savage Worlds.