I looked at the "blocks and boards" method of raising the boat. I also showed it to a couple of friends who work in a boat yard, both of whom have many years of experience in lifting boats of all sizes. If the ground under the blocks was stable it might work but the potential for disaster...the boat slipping sideways or a piece of wood shifting at the wrong time...is very high. They agreed that it might work but they wouldn't try it. They did express interest in watching it done, just for the entertainment value.
The guys at the yard use a large forklift with long forks and heavy slings for lifting. Plus, they have insurance if things go wrong. No muss, no fuss, and it only takes about an hour. That includes coffee and donut time. For what they charge to lift the boat, set it on solid boat jacks, and reset it on the trailer or in the water it’s a bargain.