OK.
I have a dm7020hd too, which has several smargo readers, and I had the same problem with USB ports swapping, I managed some time ago to rename them, using a file (/etc/udev/rules/31-smargo.rules) which had the following text inside:
SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{serial}=="Reader 74", SYMLINK+="smargo1"
SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{serial}=="Reader 63", SYMLINK+="smargo2"
SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{serial}=="Reader 3", SYMLINK+="smargo3"
SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{serial}=="A8007wrQ", SYMLINK+="te21usb"
SUBSYSTEMS=="usb", KERNEL=="ttyUSB*", ATTRS{serial}=="A7031F41", SYMLINK+="easymouse"
So now, on softcams I replace /dev/ttyUSB0,1,2,3,4, with their names (/dev/smargo1,2,...), and the problem is over.
But now, talking about tuners, I know i should "rename" tuners, but don't know how.
Besides, I see a udevinfo command, and none of my machines have it inside.