I've got a thundercat frontend on the fazer and due to the forks being longer they stick out the top considerably anyway so attaching them is not a problem for me, I'm not suggesting to use thundercat clipons on a standard front, just obviously that's what I can do!
At standard they would foul the tank, I have Genmar bar riser plates which raise it a little but I don't think enough, I'm considering several options, I'm not liking the angle of flipping the clipons so I'm thinking of getting another top yoke and grinding it down as a riser plate!
If you get some clip ons with a high enough built in rise you would mount them under the top yoke!