I feel your pain. I actually tried fishing line, and it didn't work well. Best solution I came up with was to take a little stick (actually mine was a busted off part of some latticework that was a few inches long), put the stick below the lnb between lnb and arm, and then take some electric tape and/or some thin wire (careful not to overdue it so you don't block your signal) and wrap that around the stick... may have to add occassional wad of electric tape as more support. Be sure to at least tweak the lnb a bit before doing all of this.... If you get it all done right, it should work perfect. May not look pretty, but who cares.
It's not the strength of the arm that's the issue really... it's the weight of the lnb shifting due to gravity. By adding more support between the arm and the lnb's big base you help let gravity help you instead of work against you.
