How to design Rfb.up and Rfb.down to get the certain CVCC output in LNK616?

I know PI has a SW to design their value for LNK616, but It will not do good to the designer.
I know the relation between them should meet the setting Vout, that is, (Vo.max+0.7)/No*Nfb*Rfbup/(Rfbup+Rfbdown)~=2.0V, then how to define the value of them to get the required CC output? I know larger Rfbdown can make larger Iout at CC mode.
DOes anyone have a experienced rule, formula or figure?
Thanks!