Low Vov problem in LNA design

For a low power LNA design, for example Id=0.5mA, L=0.18um, it seems there is a critical tradeoff between Vov and W,for w=40um,Vov<100mV from my simulation result, for w-20um,100mv<Vov<200mv,but the noise performance is degraded. Is there any problem with a low Vov voltage? Should I used the w=40um or 20um one to design the LNA?
The smallest size RF model I have is W=5um,F=8, so if I used smaller value than that, do I have to give new values to the parasitic components of the model?
Thanks very much:D