I worked in a yard that only had a travel lift on rails - it could not drive around. We routinely blocked boats up to 40' on a trailer, so your situation is actually quite easy since it is a light boat.
1. Keep the boat on the trailer, block the wheels to keep it from rolling.
2. Stack wood blocks (12"x12"x12"). I know that these are hard to find, but cinder blocks are notorious for crumbling. Since the boat is light, you may be able to get away with it, but BE CAREFUL!
3. Put a stack of blocks under one side of the transom with a 12" square pad under the hull
4. On the other side, put a stack of blocks and a 4 ton-ish hydraulic jack. Jack up the hull support with a stack of block next to the jack.
5. Repeat #4 on the other side of the hull.
6. Repeat 4 & 5 until the hull is the enough.
7. If anything seems unstable, STOP and adjust accordingly
The centerboard should not support the hull. The pivot pin will not take it.
Sabre 38 "Victoria"