BBill,
We bonk them enough to slow them down a good bit, bring them over the side, and then cut the gill area - on both sides if I can get them flipped over. If we bonk them totally into oblivion they don't bleed as well. With a somewhat limited amount of bonking, even on big ones, we've never had a serious/dangerous level of flapping around in our 22 and 26-footer's cockpits.
We've brought in lots of 30 to 70lb-ers that way, and a couple of 100's over the years, using a wireman's gaff and a weighted bonker. They do their serious thrashing around while they're still hanging on the wireman's gaff over the side - so far I've not ever lost my grip on it. I let them wear themselves out a bit while I hang on, then use the bonker after they calm down some.
Never tried the tail slit - maybe that's a good idea.
Richard Cook
New Moon (Bounty 257)