ABYC is silent regarding Navigation light placement relative to the shear. So are the international standards as of htelast time I checked.
16.6 REQUIREMENTS - SPECIFIC LOCATION AND INSTALLATION
16.6.1
Lights shall not be obscured by the hull, deck, fixed structures or optional equipment under normal operating conditions.
EXCEPTIONS:
1. In accordance with the 72 COLREGS and Inland Rules, all-round lights may not be obscured by masts, topmasts, or structures within angular sectors of more than 6°.
2. Anchor lights, which need not be placed at an impracticable height above the hull.
16.6.2
Navigation lights shall be installed
16.6.2.1
to prevent the lights from shining into the operator’s eyes when the operator is in the normal operating position, and
16.6.2.2
to prevent reflection off a vessel’s structure within the operator’s field of vision. See FIGURE 4.
NOTE: This does not cover reflected glare or loom light from atmospheric vapor, such as fog or mist.
16.6.2.3
The luminous intensity of navigation lights shall not be adjustable by any variable control.
16.6.3
The all-round light output shall not be directly visible from the operator's position. See FIGURE 5.
16.6.4
Light fixtures shall be mounted to ensure that the light shows over the required arcs of visibility, and shall satisfy the required vertical separation and location requirements when the vessel is in a static floating position, or when measured using the datum water line as a reference. See FIGURE 6 and FIGURE 7.
16.6.5
All craft on which navigation lights are provided shall have an anchor light. The anchor light need not be permanently installed, but shall comply with A-16.5.1.
16.6.6
When a vessel uses electric lights, one operation, such as one switch or one position of a switch, shall display the complete navigation light configuration as required for the vessel while underway. Another switch or switch position shall display the anchor light only. Switch functions shall be appropriately labeled.
EXCEPTION: Auxiliary powered sailboats may use additional switches to satisfy underway conditions for both sail and power.
16.6.7
Navigation lights shall be mounted so as to minimize damage by contact with other objects under normal operating conditions.
16.6.8
Navigation lights shall be installed in accordance with ABYC E-11, AC and DC Electrical Systems on Boats, as appropriate.
NOTE: ABYC E-11, AC & DC Electrical Systems on Boats requires that conductors used in navigation light wiring be sized for no more than three percent voltage drop.