I account for my high percentage of deep hookings to (1) my relative lack of experience with crab flies and (2) the way I fish them most of the time as a shore schlepper. I started using them about four years ago (?) and like I said the year before last was the apex. When I fished them blind, which I did mostly, they would be taken deep. When I played cat and mouse on Monomoy, they would usually not - although I did experience some deep hookings even when set quickly on sight hooked fish not nearly the same percentage.
I fish them blind by casting them into a hump sequence in a moving tide and walking them up a ridge, then letting them slide down into the next hollow with the current. Absolutely DEADLY. Unfortunately, with the force of the current pushing on the line and the fact that it's a blind presentation, I hooked a lot of fish deep in the crushers and stopped doing that despite it's effectiveness.
When I sight fish the flats, I still use crabs with regular hooks. Last year on Monomoy, my son and I were walking crabs in front of some huge bass one summer day. He had a cow playing cat and mouse with his crab right up to the leader. It was awesome watching him experience the same kind of intense anticipation I do in the same situation! The fish turned away when it saw us.
Steve, your comments make me realize that (a) you are fishing from a flats boat (b) sight fishing afficionado (c) experienced with crab fly fishing. Therefore you are probably getting the hook set quickly upon the take.
It also makes me realize that the deep hookings were from blind crab presentations "in the humps". Therefore I think the application where circle crabs play the most important role is in the latter.
That's a valuable introspection because it will give me comfort in fishing the humps with crabs again using circle hooks this season.
Note: using the deep eel in this situation produces like mad and I have not had any measurable precentage of deep hookings with them. Maybe the shape has something to do with it as well as the eating technique?