Yes, they are handy for lifting trailers.   The fifth wheel will lift them fine as long as you don't do anything stupid like push a half loaded trailer off of the blocks by trying to lift it without the brakes set.  Then the air ride looks VERY nice...especially when it's 11:45, 105^o, and you are hungry!

ALWAYS hook up the trailer air before you try to back under!   You shouldn't have to ask how I learned that!