The only way to fit it is the normal way that you would fit a kineton with a snaffle i.e fit the bit as you normally would with a slight wrinkle in the corners of his mouth. Then put the kineton on so the metal loop sits flush around the bit & is above the nostrils like a well fitted drop noseband across the front of the face.
TBH I wouldnt be that keen on this combo as the whole point of the gag is for the bit to get higher in the mouth when you pull and you will either find it slips out of the curve of the kineton or it pulls the kineton up with it producing a very very exagerated action which would be slow to react when you give a horse its head.
Thanks. I will try the Kineton and the gag at different times to see which one is the most effective. Will try the Kineton with a waterford snaffle in fact.
Agree with Joss. Also you can alter the fit of the kineton slightly to control how quickly it acts - if you have the part across the nose shorter, then it will come into action with less pressure down the rein - longer and you will need more rein to have an effect on the nose.