That's the scary thing about fishing big water, the lakes I have been on are 500 acre or less and have very even ice. The big lakes around me 3,000 - 5,000 aces can have shore ice and bays with 8"-9" but out in the middle of the lake only maybe 2" of ice. Every year idiots from out of state come up here for the christmas/ new years holidays and end up falling through with there snowmobile or pick up truck, they think because the lake is froze over we have had ice for weeks, not so. Same thing every year.