Double key lime pie filling and increase from 9" to 10" shell, new baking time?

Since you increased the thickness, you likely need to reduce the baking temperature somewhat (perhaps 25 degrees?) and bake longer. My best guess would be 25-50% longer, but you'll want to just start checking for doneness sometime around the original baking time. It should be mostly set but still a bit jiggly. If the crust is cooking too fast you can also cover the edges with foil to keep it from browning too much or burning.

The amount of time the filling needs is determined by the thickness of the filling. Going from 9 inch to 10 inch increases the area with (10/9)^2-1 = 0.23 = 23% . I would therefore suggest to make 25% more filling (this will result in the same thickness of the filling) and use the same baking time as you normally use for your 9 inch pan.

The thing about recipes with baking times, whether they are for pies, cookies, poultry, or whatever is that the predicted time is only a best estimate on the part of the author. They are a guideline to get you started--but there should be a test or indicator to let you know when the item is truly done.

In the case of the pie, the recipe author cannot know what type of pie dish you are using, how thick your crust is, what temperature oven is exactly, or what temperature the ingredients were when they went into the oven. All of these things may affect the actual time it takes your pie to finish.

Key lime pies are essentially custard pies. Most custard pies should be cooked to 180 degrees Fahrenheit, at which time the filling will appear mostly set, but still quite jiggly in the center. Martha Stewart's recipe, for example, says "bake until the center is set but still quivers when the pan is nudged."

You should be fine if you use these tests to determine when your pie is really done. Since your pie is quite full, you can probably start checking around the original guideline time.

Good luck and enjoy.

I just made the same pie--10" with double key lime filling--and I had the same question you posed. I baked mine 15 min at 350, then reduced the temp to 325 and baked it til the internal temperature was 145°F, which is what I read it should be on another site. (I think that took about 10 more minutes of baking.) The crust was browing a bit too much and covering the crust edges with tinfoil was a challenge to do without nicking the custard, so next time I make this pie, I'll bake it the whole time at 325 and use the internal temp as a measure of when it's done.