rnvinc,

I'm speculating that if the foam is attached, it will better keep the lid upright. It's just a speculative hunch. It would rub against the rope if tilted and would not allow it to tilt too badly...such as if decaying material on the bottom was emitting bubbles and they were catching in the rim....trying to tilt the lid. I am just guessing....very good question and questionable answer. Lol, Good Fishing, Mac

UPDATE.....UPDATE

First of all, the material change.....I found out from a poster that the fun noodle will take on water when submerged over a period of time. We siliconed 4 blocks of styrofoam under each lid....each little block was 3/4 inches thick and 2 X 2 inches in size. The brick still was very sufficient for anchoring the attractors. The TVA wouldn't allow the plastics in the reservoir so we contacted the rangers in the national forest....they liked the idea and planted the attractors in a mountain lake on an experimental basis. We planted 75 in 9 groupings of 5 and 10. Come September, they will survey the use by the fish by running a shock boat over the top. They were planted under the supervision of the fish biologist at a depth of 8 feet, and were dropped near changes in the bottom at that depth such as small channels and humps.