DEC Pro380 RX50 boot frustration

I have been trying to boot my Pro380 from an RX50 and can't seem to get it to work. I have to be missing something. I have been using RX50 floppies that work fine in an -11/73. When I put those disks in the Pro I get an error code that translates to "Bad format or blank disk." and a picture of a floppy with a question mark. I created RT11 boot disks for the FB monitor and used the COPY/BOOT:DZ thing to get the right bootstrap. All on a real -11/73. I was able to initialize a volume on the diskette using P/OS from the Pro's hard disk. The resulting disk boots in the -11/73 with the message ***THIS VOLUME DOES NOT CONTAIN A HARDWARE BOOTABLE SYSTEM ***. In the Pro it gives me that same error code 340. The fact that this message was created by the Pro makes me think there is nothing wrong with the hardware or the floppy format. I have swapped floppy controllers and RX50 drives with no change. I have downloaded a couple disk images that I thought should be bootable (P/OS maintenance utilities) with the same results. I have a little less confidence in this because I had to convert .td0 images to binary images to copy to the floppy. I did find a note about installing 2.9bsd on the Pro that indicates that the floppy must have a special header for the bootstrap different from the NOP and BR that the normal PDP-11's usually require. Shouldn't this be taken care of by the RT11 bootstrap installation process? Is there something that needs to be in the first track that is missing from my disks? This Pro380 was a VAX console. Is there possibly something different about the firmware?