i have see those pieces used under the spiders but not between the spider and cone on a papar cone. wouldnt use it.
notch ur cone so it fits over the leads easy. then put a heavy bead of ca around the former about 1/4" off where the cone sits. drop ur vc in the gap about center(no shims). push ur cone over the former, it will push the ca glue down and spread it on the cone and make a nice glue joint. spray will acc. remove recone assembly. now mix up some 5 min epoxy and pour it thick around the cone and former on the front of the cone. let it sit and dry couple hrs. then recone like you are use too...