Nice to see that you're liking it. At the end of the day there are a lot of reinforcements incoming for the Allies, can you check if the game speed is still manageable on your end. In ran into some slowdowns and would like to remedy that.
The game slowing is a symptom of the smaller grid size.
If I understand it correctly, the smaller grid size affects the number of calculations necessary to define routes, visibility, and combat fire.
It's subtle, but I've noted that routes which are defined on the map for highlighted units appear to be more detailed than in larger grid maps when I'm playing at the closest zoom level. Each of those turns is a calculation that had to be made against the grid pattern. Similarly, sighting and combat fire effects take into account more terrain obstacles on a 25-meter grid than on a 100-meter grid, making the calculations more refined, but also slowing the pace of the game.
Despite that, the game is still intriguing and engaging.
But, as Simovitch points out, it's worth a review of the pluses and minuses from the play to determine whether the 25-meter standard can provide the same kind of response as the default game standard.