Not knowing what you have in the bottom if anything to hold it down. I would think about movement. We have some in Wylie and they are stationary with two-foot section on the bottom with cement to bury in the mud when dropped. Also, the top has a 2-liter bottle inserted with the cap down so to help hold the air longer period of time and hold it up right. I'm thinking if you have deep water, it may be better to have it on the bottom so crappie can adjust to their comfort zone and add one above it like you are talking about tied off but weighted on the bottom to help keep it from moving easily. Just thinking of course!