i downloaded, four or five of your things and they wouldn't work with any of my other add-ons, (it comes up with the message about the bumper, whatever that is)
I know i have placed it in the right spot and i haven't extracted it, its gone straight from your link to my add-on folder, still in .zip format.
and its not just one of them each one individually doesn't work, ( i downloaded the firework launcher, the scythe and the link hat, the backward hat and the afro)
p.s when i used it without my other add-ons activated they are pretty good, but they just don't work otherwise, but on there own they deserve a couple of cookies.