I think FL rolled back the law on the tag mounting...
Statutes & Constitution :View Statutes : Online Sunshine
The 2009 Florida Statutes
Title XXIII
MOTOR VEHICLES Chapter 316
STATE UNIFORM TRAFFIC CONTROL View Entire Chapter
316.2085 Riding on motorcycles or mopeds.--
(1) A person operating a motorcycle or moped shall ride only upon the permanent and regular seat attached thereto, and such operator shall not carry any other person, nor shall any other person ride on a motorcycle or moped, unless such motorcycle or moped is designed to carry more than one person, in which event a passenger may ride upon the permanent and regular seat if designed for two persons or upon another seat firmly attached to the motorcycle or moped at the rear or side of the operator.
(2) A person shall ride upon a motorcycle or moped only while sitting astride the seat, with both wheels on the ground at all times, facing forward, and with one leg on each side of the motorcycle or moped. However, it is not a violation of this subsection if the wheels of a motorcycle or moped lose contact with the ground briefly due to the condition of the road surface or other circumstances beyond the control of the operator.
(3) The license tag of a motorcycle or moped must be permanently affixed to the vehicle and may not be adjusted or capable of being flipped up. No device for or method of concealing or obscuring the legibility of the license tag of a motorcycle shall be installed or used.
(4) No person shall operate a motorcycle or moped while carrying any package, bundle, or other article which prevents the person from keeping both hands on the handlebars.
(5) No operator shall carry any person, nor shall any person ride, in a position that will interfere with the operation or control of the motorcycle or moped or the view of the operator.
(6) A person under 16 years of age may not:
(a) Operate a motorcycle that has a motor with more than 150 cubic centimeters displacement.
(b) Rent a motorcycle or a moped.
(7) A violation of this section is a noncriminal traffic infraction, punishable as a moving violation as provided in chapter 318.
History.--s. 1, ch. 71-135; s. 1, ch. 76-31; s. 9, ch. 87-161; s. 320, ch. 95-148; s. 7, ch. 96-414; s. 164, ch. 99-248; s. 2, ch. 2008-117; s. 4, ch. 2009-183.
Note.--Former s. 316.108.