Lotsa ways to skin a cat. The "100sq ft of copper" is an urban legend...repeated in many, many places but nevertheless nonsense as is the impreachment that "wires won't work".
What is true is that you need some sort of effective RF ground to serve as the "other half" of the antenna system. This can be as simple as a wide copper strip run from the tuner to the nearest bronze thru-hull. The thru-hull should not be otherwise bonded to the DC system or, if it is, it's a good idea to put some sort of DC-blocking device inline, like a number of parallel capacitors bridging a narrow gap. Type X7R Monolithic Ceramic capacitors, 0.15uF, $0.91 each, Digi-Key part number P4911-ND would do the trick nicely. See Stan Honey's excellent article on grounding here: Grounding
Also, see my post on "RF grounds in the marine environment" here: SSCA Discussion Board :: View topic - RF GROUNDS IN THE MARINE ENVIRONMENT
I don't know the YoungSun 35, but there may be other ways to fashion an effective ground as well, including: stainless steel rub rails (like the IP's have), pushpit/lifelines/pulpit complex, radials under the decks, aluminum toerails, etc., etc.
But, the simplest and pretty effective way to do it is just to run a wide copper strip to the nearest thru-hull. You can add to that later if needed.