To use the banjo you gotta get the conical seat out of the caliper. On 750's it should be able to be knocked out, 400f, not so sure.
Either way slingshot is the way to go. If you are willing to sit on it for about another week he will be back from his hiatus. He said he has been burnt out, that's why the site is down. Another advantage is that he has experience with all of the combos, lengths and angles necessary for the bikes and combos.