I've done a few sets of slash cuts as well. I used a regular bi-metal hole saw, no extensions or anything.
First, wiggle the tube around til it falls out. Then get the largest hole saw that will easily fit in the pipe. When the baffle plate is cut through, don't go in any farther, the mesh lining will get all bent up. Knock out the next baffle, pull it out with stiff wire hook. I used pencil rod (1/4"). I clamped vise grips onto the wire after it was hooked, that gave me something to hammer on to get the baffles past the hanger nuts and the smaller diameter remains of the end baffle. If you want the last baffle out, you can cut it out around the perimeter with a home made long chisel like Shutter described.
The two end ones are in there solidly, the two middle ones will knock loose easily.
