I'm not real sure what the article is referring to (don't subscribe to I-F anymore) ... but, when using a float/bobber/cork (whatever you want to call them), I always use one that "slips". My longest poles are only 8ft long, so a clamp on type float is tough to use - if you're fishing deeper than 10ft. Plus, it makes it a bit difficult to "cast" ... if you're "required" to do so, to get your bait into a specific spot, that's any distance away. A slip float allows you to fish from just under the surface, all the way to the bottom (however deep that may be, and if you want to go that deep). The only trade off, with slip floats, is getting a "stopper" that won't hang up in the tip eye, won't hang up in the line spool, and will freely & easily pass thru the guides/tip of the rod you're using. I've gone from using the "bobber stopper" type (rubber stopper/bead on a wire loop) to the plastic "band with holes" type. They both have their respective pros & cons.
Do slip floats work - you bet they do ... but, just be sure and set the depth slightly above the depth the Crappie are suspended. Crappie will go "up" to grab a bait, but rarely go "down" to grab one. If your float starts moving off, but doesn't go much below the surface - you're fishing on a level with the Crappie. If the float comes up (falls over on its side) - your fishing a little too deep. If the float bounces, then proceeds to "head towards the bottom" - you're right on target !! ......... luck2ya ...cp