You may be able to go larger but 160mm front and 140mm back is probably already more stopping power than you need. That is what is on the Quest which is heavier than the Silvio and they are easy to lock up if you want to, especially the back.
Good stuff to have known BEFORE ordering parts...when's that 2.0 assembly guide going to be out anyway?I can't guarantee a 160mm rear will clear the seat stay.
140mm was the intended rear rotor size.