They are only meant to used to keep the mower from bottoming out. They should not be run to hold the mower up, but rather about an inch or so off the ground. Use the hydraulics to hold the mower up, especially on rougher ground.
'60 FH Lo-Boy
'57 FH Cub "Rusty"
(2) '48 Cubs
'75 IH 140 w/1000 loader
C-3 mower, FH Woods 42F, 22 sickle, 54A blade, L-54 blade, 194 plow, FH L-38 disk, FH LB disk, 144 cultivators, FH platform carrier