I have never parked my 31' fifth wheel on a steep hill but I have been on some gentle inclinclines. I use a single $3 chock on each side. If I am not sure which way the grade runs, I'll put one in front on one side and in back on the other. I have also used... ... ... ... ...
Ramtough:::: The use of the Chock-n-Lock type of devices are not limited to preventing the trailer from rolling. Their purpose is also to stop the "shake" that occurs as someone moves around inside the trailer. You're right about simple chocks... homemade works great and cheap also. However they were not enough in my case. My little wife... ... 5'2", 110 lbs can shake the h. . l out of the trailer as she walks from kitchen to bath and so forth. A king pin tripod (homemade), and a set of roto-chocks took out 90% of that shake for our situation. By the way, get out of the parking lots and boondock for two-three weeks at a time on uneven ground without moving the trailer and you will gain a new appreciation for these devices.