You may want to have another vehicle around that you can call on if you need them to give you a tug! Putting the boat in is easy, but a 20 foot on a slick ramp, good luck! ( I would do as another said, load up the rear with weight!) Just use good judgement! I would assume that your rig is an automatic. ( If not, and you have no e-brake, don't even think about it!) Also, you said that you don't even feel the trailer behind you except for when you hit bumps and it lifts the rear end up. That makes me think that you don't have a lot of tongue weight. If you have none to little tongue weight, you will never pull that boat out of the water. Trailer brakes would only work backwards if they were electric. However, its not a good idea to activate electric brakes underwater. I would seriously consider asking an experienced person in boat launching to help you or guide you.