I've been looking for a burning program that gives the option of not using padding for a while.
Not sure if xcdroaster used to, k3b did, not sure if it does now. You could try it. I can't use it anyway as I don't want polkit to have permissions on my systems and k3b via udisks can't find the devices without it, it's so clever it can't even look at device files when told.
I even tried mounting an iso on
/dev/loop for a copy but again the 'modern' or perhaps should be called inexperienced GUI programs wouldn't accept the device FILE and xfburn doesn't have a copy otherwise it would probably work.
I was thinking of getting the old k3b version but the underlying programs have changed so much I'm not sure it would work.
The commandline tool xorriso didn't seem to like nopadding with the cdrecord option but cdrskin worked.
cdrskin -v dev=/dev/sr0 blank=as_needed -nopad speed=12 file.iso
It's so much better being able to verify the security and integrity in one go!
The caveat is the cd may not work with all devices as the padding is default for data to get around some driver bugs apparently. Never happened to me though.