@dpstudios
You won't be able to find a clicker kit that uses the shorter tube length because there aren't any. . I have been through that.
I would not trust the App dimensions in this case.
I would suggest that you glue a black "washer" on both ends of each of your blanks .... thickness of 0.5 * (2.42 - 2.21) = 0.105"
Of course, that means you have to rework the blank and possibly refinish as well. . I realize that you may not be able to do that if you have already turned and polished the blank you want to use ... the surface would get messed up in the lathe.
There might be a way to make those washers to the exact right size and finish the edge of them nicely so that you can glue them on (extreme care required) in such a way that you don't mess up the already nicely finished blanks. . I know that if you are able to do this the brass tubes will not come right to the end but you can compensate by making the holes in the washers just a touch small. . However, I don't think that is really necessary.
But I do think you should add a tiny bit of glue (epoxy is best, I think) when you press the hardware to the blank.
Good luck !