You didn't mention what shifters you have, friction or indexed for the front. If you have rub when in the middle chain ring and both the smallest cog and largest cog, then may I suggest you adjust so that you don't have rub at one extreme, then just trim at the other extreme. Not familiar with your bike but does it have short chainstays; that can affect rub. Just keep playing with it until you are happy and it shifts well.