I'm 5ft 6" (167cm) and struggle slightly with the C172 preferring to use a cushion to see over the instrument panel; I did part of my instructors course in it and managed okay without a booster, but didn't enjoy that bit very much.
It really isn't a problem; best bet is to get a thick slab of something called "dynafoam", and run up (or have somebody who, unlike me, is safe in charge of a sewing machine run up) a cover to create a covered cushion. Avoid readily available soft foams for a variety of safety reasons. Any company supplying the gliding community will stock dynafoam.
THE expert on seat cushions on Pprune is probably Whirlybird, who doesn't post here much now, but if you email her - she is a flying instructor and flying writer rather shorter than you who thus is a mistress of the art of seat cushions in a variety of flying machines.