I throw everything in the top bunk. A 2'' memory foam pad over the mattress and a fitted sheet over both keeps them clean.
No issues with things moving around. Most everything is in some sort of duffle bag.
My dive gear, archery gear, fishing gear..whatever I am using the motorhome for....gets stored up top.
Since it's a 20' motorhome with a bed in the back there isn't many other places for storage. One nice thing is I don't have to bend over to get at anything.