[pups] Installing Venix or 2.9bsdpro on a DEC PRO350

Hi all, after having downloaded both distributions from a PUPS mirror, I was trying to install Venix or 2.9bsd modified for the PRO350. I've created for both distributions the installations floppy using a mvaxII with an rx50 floppy. The mvaxII actually runs netbsd, so I did a dd if=floppy.img of=/dev/rx0a for all the floppy images of the distributions, but when I go and try to boot the bot floppies of venix (and 2.9bsd too) on the PRO350, they fail to boot. The drive seems to try a little then the machine hangs, no messages on the console, except a nice capital DIGITAL, no messages on the serial terminale connected to the printer port with the maintenance cable. With venix floppy instead, after failing to boot, after a litle P/OS starts from hd. What am I missing, what did I wrong ? Any hint will be greatly appreciated. P.S. I definitively want to install an ancient unix on my dec pro350..., help me ! ... Franco Tassone