Heads Ache

[37Flat]

After we deciphered right from left head, I went to work to install them. One stud on each side stripped, so they're back off. Looking closer, before I removed them, I found that #13 (torque order - 2nd from right, top row) was barely sticking out of the head. It's the one that stripped. I know I was very careful to get the right studs in the right place and have remeasured a couple to confirm. When I installed them, I double nutted them and tightened them until firmly seated.

How can one go too deep and more importantly, how do you prevent it from happening? Longer stud might help, but it seems like there's still a problem that needs to be fixed.

I know the picture doesn't really show the issue, but several of the studs seem low on both sides and I thought perhaps it's the heads are part of the problem.

What do you think?