I've just added a limited set of 2" peek-to-peek (roughly 1.75" flat-to-flat) hexmaps. Given that I don't own any HeroScape I can't say if it's compatible or not.
If anybody who owns HeroScape hexes, could attach 41 single hexes in a perfectly straight line (connected flat-to-flat, placed against a wall or something to keep it straight), and measure the entire length (excluding the connector protrusions), and report back, that would be awesome.