[JandC]

I have a 6' level that I purchased from Harbor Freight (cheap). When hooked up I simply place my 10' step ladder along side the front of my Montana where my front air is, since that is the highest point when hooked up. I level across with the level and drop my tape measure down to the ground. The DW reads the bottom of the tape measure on the ground.

The whole process takes about 10 minutes and you know for sure. It is not difficult.