Started to install the Norcold this last weekend on my 31'..Got started but got nervous when I began to drill the hole for the copper tubing. I don't want to drill a hole that I find out after its a done deal that I put it somewhere it shouldn't be...*o figured I check on this forum before I went any further. I know some others on here have installed this unit and was wondering where you drilled the hole in the icebox. I know there is a double wall and was wondering how far I'd have to go with the drill. Thanks for any info.