Seeing two vehicles yesterday, that were not displaying tax discs made old nature think that there was something suspicious going on, until I realised the new taxation scheme had come into being.
But back to the original subject, which appears to be a good idea on the face of things. Not having seen the print-outs I would not have the knowledge of what the print-outs are requesting information wise. But caution by some might be needed.
For example: User's of disabled badges normally know how to display their badges, but in some cases actually showing the photograph of the disabled person can bring its problems, in situations least expected. On a very few occasions I have seen alarm on the faces of those disabled badge holder's, when I have explained possible outcomes regarding display of information to other member's of the public.
If you look at the PDF link from the article, you fill in Emergency Contact Information and Medical Information Then fold it so that the outside just reads 'Emergency Contact Disc' and so no personal information is visible, then slot it into the Tax Disk Holder.
"Isn't the UK tax disc to only legal obstruction permissible on a windscreen?"
Haven't recalled seeing or hearing about any prosecutions regarding sat-navs, incident cameras, but there might have been a few telling offs for having flags, boxing gloves or large air re-fresheners hanging off the rear view mirror :O)