PDP-8: anyone tried NVRAM simulation of hard drives?

Has anyone had interfaced nonvolatile RAM to a PDP-8 to simulate an original hard drive? The DF32 fully expanded with four disks was only 256k x 12... Dallas Semi makes battery-backed NVRAM in a variety of sizes. Two DS1258 (each 128k x 16) would make for a very simple interface that would fit on a single card (or at most a double card). Packing the 12-bit words would complicate the interface a little but lower the cost of the NVRAMs. Using an old 3.5 or 5.25 inch hard drive would be very cheap per meg but would also require development of a controller (like the 8051 mentioned recently as an interface to an HP computer). I don't think there were any original drives greater than 1 Mword available, so larger ones would require nonstandard code to support them anyway. Any thoughts? -Charles