Modernica vs HM dowel leg  

i purchased modernica glass fiber shell chair with dowel leg few years back.
i keep noticing the feeling when you sit on the modernica chair is slightly different than Harman Miller one.
it feels like that my weight is slightly leaning toward to backward.
and I checked carefully the differences between structure of dowel leg between two brand.
i found that the one from Modernica has front part built a bit higher than HM one. Does anyone know anything about it?
also wonder if I can switch my dowel leg from modernica one to HM one. does it fit?
thanks,
y