I know this was stated somewhere but my searching has proven fruitless. Can anyone direct me as to where I can find the minimum required thickness for winter activities. I am a little concerned with being out in the broads with only 7-9" of ice and four snowmobiles. I suppose as long as we don't stop all together, we should be ok, but, I'm not comfortable with this. We were out there this weekend with 4 sleds abreast, but I truly thought there was a foot of ice. I am not into "Skimming" so any help would be appreciated.