I really don't know why we still have tax discs here, as all the info on your insurance, tax, license and MOT is all accessible via the police national computer; which is why they sit around with ANPR cameras/vans...or am I missing something?
I ve got the same ish tube for mine, mounted on the swingarm, I cut the metal loop off as it was too short and mounted onto a rectangle of carbon fibre I cut from an old bit of fairing. Its discrete but visible to traffic wardens etc.