Skinny end points at the head. If you just slip them in, they will probably rattle. I'm opposed to drilling holes in my pipes, so I'd try to be creative with the install. Try bending the flanged end out so they fit snug/tight and have to be "tapped" in, JB Weld, or if you have access to a welder, I weld the nuts to the inside of the flange then also put the bolt in from the inside. When you tighten the bolt it acts like a set screw against the exhaust pipe- no holes. that or just weld them in. I mocked up my baffles dozens of times before I got the right combination of sound volume and performance. Once I got it right, I just tacked every thing in.
Mount everything up and try it out before you make anything permanent.
