At a first glance, you would think that Ultimate/SD cart is not just the perfect companion for providing a multi-gigabyte, programmable $8000-$BFFF rom space, but also a great way to leverage the 800/Incognito's unique architecture, where you can run its internal Hard-Drive (and resident DOS & loader facilites) independently of your cartridge-ports, thus leaving you free to use them with ANY cart of your choice.    It all sounds beautiful... until you plug it in and fire it up (as