I store mine on a cement garage floor that drops 12.5 inches in 30 feet across. The truck camper is level and each jack is at a different height. It sits like this for at least 48 weeks out of the 52 in a year and sometimes more. As you can see in my SIG that it just makes it under the top of the metal garage. Except being out in the weather at the dealers lot before I bought it has been out in the rain 1 day at Mardi Gras 2012. The rest of the time, for 3 years so far, it has been high and dry every day of it's life except for that 1 day. On a slope, as long as it's not a big slope should be no problem. I don't see any numbers so we know how much the slope is. Hope this helps.