I have the same problem with stock fit. When mounting a Pach Decelarator pad on a Ruger 77 stock, I also mounted a 1/4" black spacer made by Pach. Since the Dec. pad was 1/4" thicker than the original Ruger pad, I increased the LOP by 1/2". But I still needed an additional .75" for an ideal fit.
But before I made any more changes to the stock, I decided to practice shooting with the stock as is. Every fall before hunting season, I engage in at least two or three rifle practice sessions using field positions (mainly sitting and standing.) To make these practice sessions as realistic as possible, I wear my normal cold weather hunting clothers: long underwear, fleece sweater, and down vest or insulated jacket. I then put on my small day pack (with unpadded shoulder straps which do not interfere with shouldering the stock.) With my fall weather hunting clothes on, the stock fit pretty well; and my practice shooting sessions went very well. Under those conditions, the LOP was just about perfect.
Then I remembered my custom stock maker friend from my teenage years, and I remembered what he told me about LOP. He said the classic fit test for LOP involved holding the stock and checking how well it fit into the crook of your elbow. He said that mainly tested the fit in relation to the length of your arms. He went on to explain that the length of the shooter's neck is more important than the length of his arms in determining LOP. He also said the shape (and fullness) of your face, your overall build (fatter or slimmer,) the thickness of your hunting clothes, your shooting style, and your shooting position(s) also had a great influence on the LOP needed.
His method for checking LOP before building a stock, was to have the shooter put on his hunting clothes, and go shooting with the stock maker who would bring several rifles with different styles and sizes of stocks. He discovered that many shooters need a different LOP than the LOP indicated by the crook-of-the-elbow test.
So it was for me. But my stock still felt too short for some positions in my normal clothes. Since the rear surface of my recoil pad was almost perfectly flat, I decided to just slip a Limb Saver slip-on pad on over the installed pad. Everyone told me it was a bad idea, but in my case it worked perfectly, especially for bench shooting with normal clothes. The extra recoil absorption was much appreciated, since my M77 was a .300 Win.
The system worked so well for me that I decided to use the slip on pad for normal shooting weather at the range. Then I remove the pad when I wear thicker clothes for hunting. (This also helps me shoulder the rifle more quickly while hunting.) The system also allows shorter family members and friends to shoot my rifle easily, and it won't be a specialized stock that won't fit most shooters in case I decide to sell the rifle or hand it down to a nephew.
To make the system work better, I sanded off a slight amount of the material near the toe of the permanently mounted pad to make a perfectly flat surface. This made the pad fit perfectly with the slip on pad.
I don't know what will or will not work for you. But I do recommend that you refrain from letting the crook-of-the-elbow test dominate your thinking about the LOP you need. Try the fit of your stock wearing different clothes while shooting in different shooting positions. Observe the clearance between your eye and the scope when you do this. Also observe the comb height to see if it needs adjustment. It's often the case that a long armed shooter also has a longer neck and requires a higher comb. Proper comb height is very important when using a scope sight.
It's possible that you may decide that you don't need to make any permanent changes to your stock, or you may decide that you need to make smaller or larger changes than you originally thought.
Good luck.