All of this makes me want to say "shin conditioning" as the answer.
I highly recommend taking note of where the impact areas are when you are kicking someone's leg and when you are doing leg checks. Then condition those areas as a priority. You'll want to condition all of the shin, but certain areas will need more attention than others.
The angle of the shin is determined by the technique being used. You can probably have someone hold a staff and you can lightly kick that to get an idea of where your impact areas are. The kick should be natural as what you use vs formal as what you would do in kata. After you kick the staff, have your partner lightly swing it and leg check it. Once you make note of the impact areas, then verify it in sparring to make sure that those are the areas receiving the impact.
The only real con is not to have conditioned shins.
Thanks, I fully get the point of conditioning and I think both body and mental conditioning is important but this in dependent of technique.
I was thining about speed/power and the knees side forces? As you say the part of shin that hits depends on the technique, but i can also choose my technique; thereof the question.
I personally think the flat part feels better, but not for the shin itself, but because
+ it requires slightle less internal hip rotation, and less turning on the food, but uses insted more "body rotation", so I feel like i get more rotational energy into the kick. and it thus allows for faster recovery as i don't end up as much sideways.
- It is maybe a little slower? less snappy, but instead more power. And for this is good as some hip rotation is difficult for my back.
- But at least in theory, it should logically give more sideways backreaction into my knee joint on the kicking leg. But i haven't ever felt a problem, but it wonder if it may come with time?
Maybe most people don't analyse things as much but I wonder if someone had any input on this. I found recently that active thinking about NOT trying to land on the sharp part of the bone, but actively aim for the flat part, and instead raise my kneed earlier to create horizontal momentum from body rotation makes it easier and it feels better.
I think the choice depends also on your hip flexibility, but the question is which is faster, more powerful and better for your knees?