Whatever they're doing down there I believe that being slow on the hookset, not reacting to the very first bite you feel, is what ends up with body hooked halibut.
My technique is to take a crank or two on the reel, tighten the slack, load the rod, then set the hook. If it's shallow you can just lift the rod to load it up before setting the hook. Either way results in more hook ups and rarely, if ever, a body hooked fish.
When a decent sized halibut commits to eating a jig they'll take the whole thing in their mouth. If they feel something out of sorts they'll spit it out. If you're slow on the hookset and they've spit it out that's what results in a body hooked fish ... in most cases.
I'm a firm believer in using the lightest jig head you can get away with. Six or eight ounce heads will catch more fish than heavier heads. With heavy heads they don't hang on to the jig as long. A big chunk of lead doesn't feel right and they'll spit it out quicker than a with lighter jig.
Don't get me wrong. I'm not saying that halibut won't bite a heavier jig. They can't tell the difference until they get it in their mouth but having a few more seconds to react to a bite, before they spit it out, is what makes the difference. Bigger fish may not be as sensitive to heavier heads but average Cook Inlet chickens are.
Another thing that helps to reduce missed bites and actually catches more fish is less jigging. One or two sweeps of the rod, "jigging it", and then let it sit for fifteen seconds or more. The jigging motion attracts fish and when the jig is stationary, with just the tail swimming, they'll latch on to it.
Halibut will hit a jig that's rising and falling but pausing it seems to tease them. It's also easier to detect a bite when you're not jigging up and down as much. When you pause keep the rod tip low so it's easier to sweep the rod and set the hook.
I've seen larger halibut appear on the fish finder, jig once or twice, and then a second or two later ... boom ... hook up. It works.
I use jigs in 2 situations.
1. Shallow water drifts in heavy current.
2. When I get a big fish under the boat that won't commit to eating a baited circle hook.
I never have my clients "jig". I have them mooch. Hit bottom, come up 20ft, drop, repeat. When I'm in one of my big halibut potholes in heavy current, it works wonders. And as far as detecting a bite.. you can barely hang onto the rod when one jumps on, let alone get a hook set in. A lot of those bigger halibut will hit it on the way up, as far as 20ft off the bottom.. A pink jig with some salmon belly on the hook will imitate a salmon very well. And that is what they are after this time of the year. They lay in heavy tide rips 60-150ft deep, picking off the salmon as they get washed across the rocky rips. If you jig close to the bottom as you are getting washed across the rips at as fast as 3kts, you'll get stuck. When they hit up high, hold on, as they'll want to go down that 20ft in about .5 seconds. Interesting too, that you don't know if it's a 40lb hali or a 120lb hali until a few minutes into the fight. They all run like hell in that shallow water current.
Yesterday we got a 110, 90, 70, 60, 60, (all of which had to be released) and we kept a 43, 42, and 40lb halibut for the 3 guys I had.. using the technique mentioned above. All in an hour and a half. Did the same thing 3 days ago, and had similar, but a bit bigger results.
Unless I find a pothole with a bunch of big hali, I can always get a bigger sized score by not using jigs, and using something with more scent.