As a former dealer who has raised sailboats with all various type of lifting to include a crane with two long straps from a single attachment point or hook, I will give you some pointers as the largest was nearly a 33 footer with a mast of 55 feet in length rigged in the upright position over a bridge.
First, I would err on the side of safety using wider and higher tensil strength straps but that decision will be left up to you. Assuming you are lifting the boat off the trailer without the mast up. you would want to have longer straps so not to crush the hull inward which I would be concerned with the 30 footers as they are not long enough. Secondly, I would not do this when there is a lot of wind. I would have lines attached to the bow and transom so the boat will not turn on you when lifting. Make sure no one is on the boat nor below it when lifting. Most important you will need a line secured to the straps on each side from forward to rear straps to ensure that the straps will not slip out from beneath the hull. I would encourage you to also put carpet between the straps and the side of the hull so they will not mar the gel coat finish.
When you first raise the boat, see if it is level. If not, put the boat back down and readjust the straps on the hull. You will have to readjust the lines securing the straps on each side.
slowly rotate the mechanism or lifting unit over the water making sure the boat is away from the bulkhead and let it go down slowly. Have an experienced person operating the lift.
Again it is better to be safe and not stupid exercising good judgment in this type of launch.
