Boiling Shrimp

I can boil crawfish and crabs with the best of em, but always seem to have my timing just off on boiled shrimp. I picked up 5 pounds today and after boiling some were just a touch mushy on top where the vein is. The rest of the shrimp was firm, it was only the part right on top where the vein is that got mushy. I assume I undercooked them slightly. Other times I overcook them and the shell sticks. I only get them perfect once out of every 3 or 4 times.

There is a very narrow time window where it seems they are perfect. What I did today was bring the water to a boil, put shrimp in, left on heat for 2-3 more minutes, took off heat and soaked for 5 minutes. These were big 16-20 count shrimp, with a good bit of them being in the 11-15 count range.

Other times, when I really don't feel like trying to perfectly time the cook time I just peel the shrimp ahead of time and put them peeled in the boil with the shells and all. This always works well and the spice soaks up well this way. But it kind of takes the ritual out of it when you're not peeling while eating.

So what's your method?