Thought I would wade in on this one.
My 66", 42# @ 30" Blacktail TD recurve shoots a variety of 32" aluminum arrows with different tip weights. The two best are a 2213 with a tip weight of 160 grains and the finished arrow weighs 535 grains. This comes out to 12.73 grains per pound for the 2213. The other arrow is a 2215 with a 175 grain tip weight and the finished arrow weighs 579 grains. This comes out to 13.78 grains per pound for the 2215. No matter what target material, out to 25 yards, the 2215 "always" penetrates deeper than the 2213. I don't take any shots past 25 yards.