I would not trust just putting the hose on the copper without a fitting and a barb fitting. Not sure what ABYC says about it but I would not do it.
Agreed. ABYC is clear, you cannot place a fuel supply hose over a smooth pipe (there is an exception for fill hoses), it must include serrations, barbs or a bead. Only one clamp is required for fuel hoses other than fill lines.
The Standards say...
33.11 CONNECTIONS - FUEL HOSE
33.11.1 Flexible hose not equipped with permanently attached end fittings, such as swaged sleeve and threaded insert, shall be attached with corrosion resistant metallic clamps.
NOTE: Some USCG Type A hose is not designed to be clamped.
33.11.2 The ID of a hose and the OD of a connecting spud or fitting must meet the specification in H-33 Table II.
33.11.3 Hose shall not be installed on helical threading or knurling that provides a path for fuel leakage.
33.11.4 Clamps depending solely on the spring tension of the metal shall not be used.
33.11.5 Clamps shall be installed to impinge directly on the hose and shall not overlap each other.
33.11.6 Clamps shall be beyond the flare or bead, or fully on serrations where provided, and at least 1/4 inch (6mm) from the end of the hose.
33.11.7 Hose used in the fuel tank fill system shall be secured to pipes (smooth pipes acceptable), spuds or other fittings at each connection, by at least two corrosion resistant metallic clamps with nominal band widths of at least 1/2 inch (12mm).
33.11.8 Hose used in the fuel tank vent system, or the fuel distribution and return line system, shall be secured to a fitting that is formed or machined to provide serrations, barbs or a bead with a minimum height of at least 0.015 inches (0.038 mm)
33.11.9 Hose connections used in the fuel tank vent system or the fuel distribution and return line system shall have at least one corrosion resistant metallic clamp with a minimum nominal band width as indicated in H-33 Table III.
33.11.9.1 All components of hose clamps shall have a resistance to corrosion equal to or greater than 300 series stainless steel.
33.11.9.2 Hose clamps shall be reusable.