I store mine with all six legs down and leveled. I'm glad I did, we recently had sever rain in Texas and the storage facility I keep the RV at had some severe washout. The base under the RV is dirt with rock mixed but not very well compressed. One unit with just the front legs down was on its belly because of the washout. Mine was fine, the wheels had some washout around them but the unit was stable with all six legs down.
I have since had a discussion with the property manager about proper drainage.
Its one of the few covered storage facilities in the area, so I like it, I just wish they would pave the parking area's.
2015 Thunderbolt XLR 340X12HP
2011 Ford F250, 6.7, CC, SB with B&W Companion Slider
US Army Retired