looking at my new FD closer I've realized it's actually a braze on mounted style with a shimano braze on 31.8 adapter, so I just ordered a 'problem solvers' braze on to 28.6 FD adapter. I think that will be cleaner/lighter and easier to setup than the 31.8 with a shim.
I agree, I think a braze on of the frame is a better idea, if the FD's were slotted for height adjustment with different chainrings it would be a whole lot easier!