I am not arguing that he cant use a 2inch cutting diameter or that you cant either. I am just saying that the 1 3/8 does amazing damage and why not go for complete passthroughs. The reason why a complete pass through is important is if you do not get a pass through, the arrow actually helps block the wound cavaty from bleeding which "could" lead to a poor blood trail. If, by chance, the deer was able to run far...you would want the best blood trail possible. Now if you/him are great archers...almost always hitting the double lung shot with little to no shoulder meat involved then by all means shoot the larger cut...but if you are like me, where nerves/buck fever kick in or you take an extreme quartering shot like in your case you have lots of body mass to move through...why not use the 1 3/8ths...now if you are someone fortunate to have 70lb draw weight with 29 inch or more draw length and that ultra high KE then by all means use what you want.