eric,
even if the turntable is leveled, in OP's case by putting 1" high 'lifters' under the front feet
if your rack is pitched forward under the turntable, the combined weight of all other components is also pitched forward, fronts of each piece lower than the rear, add the combined weight of my 3 glass shelves pitched forward: any vibrations will more readily rock the rack forward then back ...., it is far better to level the rack and have all the combined weight be a downward force.