I've Done It
I assume you have a swing keel. I measured the minimum heigth I would have to raise the boat to get the trailer out from under the keel. I then measured the distance from the floor to the bottom of the transom and made a heavy duty saw horse (4 support legs and 2X6 cross piece) that height. I also contoured the cross piece to except the transom. I then jacked the tongue of the trailer up until the transom set in the cross piece and kept jacking until the boat/keel was high enough that the trailer would come out. Of course to get the trailer out you have to block up the bow of the boat, pull the trailer out as far as you can, jack up behind the cross piece(s), reblock, remove the front blocks and move the trailer out as far as you can, and so on until the trailer is out. I then made another V stand to set the bow back down in. when I jacked against the hull I did so by placing a 2 foot 2x4 along the center line to disperece the weight. to get the trailer back under reverse the process. Hope this helps.
