I had it both places just to be sure.
Nice one on the stern (behind the dingy) and a simple piece of black starboard with the required size white lettering mounted to the rail on the after part of the flybridge.
If on the stern you are technically in compliance. There are no exact requirements for WHERE the markings can be clearly seen. My personal view as a former USCG LE individual... if a helicopter or approaching small boat cannot read your name/hailing port from a safe distance...then I suggest a secondary marking which is still subject to dispute. Bottom line....gray area.
CFR title-46/chapter-I/subchapter-G/part-67/subpart-I
Recreational vessels. For vessels documented exclusively for recreation, the name and hailing port must be marked together on some clearly visible exterior part of the hull.
(d) The markings required by
paragraphs (a),
(b), and
(c) of this section, which may be made by the use of any means and materials which result in durable markings, must be made in clearly legible letters of the Latin alphabet or Arabic or Roman numerals not less than four inches in height.
§ 67.125 Disputes.
The OCMI for the zone in which the vessel is principally operated has final authority in any disputes concerning the permanence, durability, legibility, or placement of a vessel's markings.