I found this this morning
(http://farm3.static.flickr.com/2597/3992058257_a215b305a3_o.jpg)
it is a little hard to see but there is some metal missing behind where the washer should be. Is it still useable? it isn't quite half way around.
Should be OK the fin isn't structural.
ok just checking, I don't want to over look something simple.