14" is a little more than ideal, but in practice, I don't believe it will be a problem for you, especially given that you are using leading links which will negate the heavier steering that the extra lead will produce.
Wheel lead is almost always the biggest compromise in terms of setup, as it is dictated by "where it fits" on most sidecars, unless it's a purpose built outfit.
Nothing to worry about.
Honda C90 custom project thing
Suzuki SV650 waiting for a sidecar
XJR1300 with Motopodd sidecar