One way you *might* be able solve this is to load in as many as you can, then convert (output them) them to a Global Mapper Grid-a tiled grid- obviously including your projection info. A GM grid uses whole numbers to enable greater compression so I'm told. And then load in the separate tile sets into one workspace. If you can't load the whole data set with a GM grid, then you've not much chance of doing it I'm afraid.
monks