The highest point of the room I've choose is by the power cable which is proud, so I've put a packer 1-2 mm higher next to it, so I'm using that as my starting point, the highest difference is about 10mm, so that's quite a bit more than a light covering, I used 11 1/2 bags first time, and I've got exactly 11 1/2 bags now, keeping in mind my initial pour and my proposed pour next time, is it going to be to thick for the mats to produce adequate heat? The only change that I can make to my approach is to not cover the power leads fully and change my starting height which will be 2 hours work wasted. What do you think, keep going as I am?