Risks of leak testing hull with air pressure


I will leak test the old Sunfish boat I have. I see there is some discussion about the level of pressure to use being very low. I have a shop vac so I am wondering if this makes too much pressure and what happens if a little too much pressure is used. What is most likely to be a problem? Will it be the foam that comes loose from the hull or is it popping a deck seam?
Have someone hold the hose above the drain hole, not sealed tight. You just want to change the pressure some. Tape the bottom of the center board trunk so you can draw a bubble over the top of the trunk.
We did a leak test the other day. We used a bike pump and sealed around it with plumbers putty. I think it worked, but we couldn’t find the leak at first. (Don’t forget to tape the tiny vent hole at the front wall of the knee well. We did.) Once we figured that out, honestly I got better results blowing into it with my mouth. You can feel the pressure coming back at you when you stop. It is a bit odd, especially when tipped upside down on saw horses. Bring the whole family to look for bubbles - they can make fun of you at the same time. Our leak was small at the end of the combing. Sealed it with silicone caulk, back in business. It was SO satisfying.
I use one of those 12v air mattress pumps from like target. very little psi. works great. I hook it to a 12v battery charger. never worried about popping a seam with it.