[HECnet] Download a PDP-11 w/o Ethernet?

An off the wall question that I'm sure somebody on HECnet will know - was it ever possible to download a boot image (e.g. RSX-11S) to a PDP11 over a DDCMP serial interface (e.g. a DUP/DMR/DMC or whatever)? Kind of like doing MOP over Ethernet, but without the Ethernet. Theoretically, three-chip boot ROM sets exist for: (XL) DECnet DDCMP DL11-E - 23-926A9, 23-927A9, 23-928A9 (XM) DECnet DDCMP DMC11/DMR11 - 23-862A9, 23-863A9, 23-864A9 (XU) DECnet DDCMP DU11 - 23-865A9, 23-866A9, 23-867A9 (XW) DECnet DDCMP DUP11 - 23-868A9, 23-869A9, 23-870A9 but I think they're on the list of "not known in captivity". De