this is correct. point being that when it sits on the trailer the boat bends, when you remove the stringers it bends more, and then when you glass in new ones you'll leave a "hook" in the bottom that will affect ride and speed.
i took some 1x2"s and cut them into 1' sections and then piled em on top of each other like lincoln logs and drywall screwed them together. u could set a house on em. set the boat on 2 of em in the rear corners and then i picked the bow up by the front bow eye with a cherry picker. (the stand in the middle is just because i didnt feel comfortable leaving it in the air overnight... you can see the rope i was picking it up with.)

i thought about a dolly but i didnt want to be $100 in the project and hadnt even touched the boat yet... this was cheap and got the job done. when i was done i just tosed em into the firepit in the backyard.