For me, the priorities changed when I transferred from shooting with iron sights to scopes. The critical issue became eye relief.
l am also taller (6' 5"), so I think I need more LOP, but in practice, maybe not. The elbow pocket test is really just a ballpark reference for me. A pistol grip can make a good LOP different from a conventional grip.
My custom gun with a spacer adjustable McM A3 Tactical (The A5 didn't exist back then..., I didn't get one until later.) measures 16 1/2" LOP. Basic rifle design ergos aren't really made for folks like us, and adjustability really becomes more like a Band-Aid. The adjustments can't change the receiver design, and maybe that's where some of the differences need to be.
One thing that affects LOP for me is bolt operation. If I want to operate the bolt without disturbing my cheekweld, I can't choke up on it and crawl up the stock. With a Long Action, its impossible for me to operate the bolt without moving my head, no matter what the LOP. This is one of the reasons I like the .223 so much, the bolt doesn't have to come back so far to do the reload (I single feed anyway so it doesn't need to come back all the way to pick up the round from the mag, there is no mag involved). Things like this are why rifles like the Enfield had removable butt stocks made to three different lengths. Smart, them Brits. When you're in the business of Empire, your rifles get a serious bit of thought in the design department. Wish..., never mind.
I'm beginning to like AR's more and more because of these (and maybe other) considerations.
Someone my height can also run out of scope positioning adjustment pretty quick; the scope can only go so far forward in the rings before there's nowhere more to go, and then we get into offset rings, and intrusion into the case feeding area. There's more to LOP than just where the hand ends up, the head is affected too; and reconciling the two can get interesting.
Positional shooting, rifle height in prone, elbow placement in sitting, etc., can become complications where LOP is concerned.
...And then, there are thumbs. Recoil and short LOP can add up to a smack in the nose with every shot; so thereafter the thumb stays flat along the side of the stock. I was issued glasses in Parris Island, but the M-14's short (way short for me) LOP put the glass lens right up against the back of the M-14's receiver, just waiting to get smacked really hard during recoil. Combine that with a thumb smack in the nose, and shooting well becomes a bit more of a chore. I ended up having to shoot my rifle qualification without either vision correction or eye protection.
Now add to all that the fact that the DI's had me painting the Platoon Flag back in the squad bay while everyone else was at the range, and my actual days on the range in Boot added up to a whopping two, Pre-qual and Qual. Bummer, but I made it anyway. My civvy Rimfire Expert status bought me a Quals score of 196. Enough, but I had hoped for more.
LOP and me, we go waaayyyy back! One size fits all..., Yah, right. Standard, typical LOP runs about 3" too short for me.
Bullpups... Man, I don't even begin to know where to begin with them...
Greg