I have often thought about making a modular board myself, but I am not sure quite how to lay it out most effectively. Many boards have too many seams for my liking. These tiles are 9" tiles I discovered.
If I make a board I think I would do 18" or 24" sides to each tile as it minimizes seams but allows for a bit of portability. I could see smaller tiles being a bit too easy to move around during gameplay unless you had a great way to connect them together. Just some musings. I really like the idea of building a board with basic modularity and easy storage...