I think there are a few factors to consider if you are using spoons to troll behind a downrigger...

First, make sure the hook is properly sized for the lure...it should allow the spoon all its action, but be big enough to get a mouthful of hook rather than just a mouthful of metal when the fish hits it. Like Neil, I think the 1/0 might be the best size for a Coho Killer, maybe a 2/0 in some situations.

Second, don't be weasly with your downrigger clip...get it on there tight! For a fish to pop the downrigger, it should mostly be hooked solidly before you ever touch the rod.

Third, use a long and limber enough rod on your downrigger to take up as much of the slack as possible that is created when the 'rigger pops.

Combine all those things together and your hit to hookup to land ratios ought to improve.

Fish on...

Todd