I shoot aluminum, and used to use washers. I ended up with a lot of bent arrows.
Now I use Judo Kondors a lot, and to bring them up to weight, I take a rubber blunt, cut the end off, turn it around backwards, and stick it on the shaft before putting on the judo. I shave off enough rubber to make weight, and since the fat end of the blunt is not against the judo, don't end up with the long arms getting bent over the edge of the washer. Works real good! I have been shooting the same couple of Kondors now for several seasons. And I stump-shoot a lot... but I do pick my targets carefully.