Agree, new ramp
As a former trailer sailor, I say don't go for any time-consuming gimmick like a trailer extender. Remember, to make trailer sailing work, you need to be able to launch and recover quickly and repetitively, or else you will gradually sail less and less because it is too hard to do. My tow vehicle was a car much like yours, and I found on a normal ramp that the rear two-thirds of my boat became water-borne at the moment when my rear car tires were in water just to the bottom of the hubcaps. The bow was still dry, on the forward roller of the trailer. Then I would winch out the bow line, allowing the boat to be pushed back so that the bow was in the water, too. For recovery I did everything in reverse, winching the boat the last foot or two to the front roller of the trailer. A steeper ramp is the only good answer with your car as the tow vehicle.
