FK: Are you stocking a hawken style gun with a moon shaped buttplate, or a gun with a flatter, " shotgun style " buttplate?
The half-moon plates are designed to be mounted on your upper arm, and that often brings your nose closer to the wrist, where you can bang yourself in the face during recoil. In those kinds of stocks, I recommend a longer buttplate. Considering where you live, I think you are probably going to be wearing more clothes when shooting, than less. You do have to make allowances for clothing, and more allowances if you are mounting the gun to your upper arm, rather than the pocket in your shoulder. The pocket is between your neck and the ball of your shoulder. If you left your elbow up , the pocket becomes obvious.
I prefer to mount guns in the pocket of my shoulder for lots of reasons. For that reason, I put a shotgun style butt plate on my rifles, even my Hawken! Most but not all hawkens were made with the half moon butt plates, however, or at least that is what I read some time back. For me, it would not matter if No Hawken can be found without a half moon buttplate: I would rather have a gun I can shoot comfortably and well, than one I can't but is historically accurate. My gun also has a LH lock, so the PC police can give me a ticket and continue on with their business. I feel a certain degree of comfort knowing that two hundred years from now, someone is not going to mistake my old gun as being an original Hawkens.
I find a shotgun style butt plate is also easier to mount and dismount without catching on my jacket. I think that if you decided to mount your gun in the pocket of your shoulder, you can consider a shorter LOP. 13 1/2" would be as long as I would want to go, and 13 1/3" would be more like it. However, your prime concern should be keeping that nose away from the knuckle of your hand around that wrist. I don't shoot with the thumb wrapped over the wrist any more, unless its a snap shot at close range, before I have time to lay the thumb down along side the wrist of the stock and on top of my index finger. Grabbing the wrist with your thumb and fingers leads to squeezing the stock, which causes tipping of the barrel, usually towards your face, so that your ball or bullet hits wide of the mark at any distance. It is also a great way to anticipate recoil, causing you to lift your head just before the shot goes off, and shoot high, ususally over the top of the target. Your thumb's job is to cock the hammer. Once that is done, let it rest. That stock is not going to jump out your forehand, or away from your fingers in your right hand.
If you are barrel chested, like many men, you also want to consider adjusting the down pitch to give you more. That is done by cutting the butt at an angle to remove a larger section of the toe of the stock. You measure Down pitch by putting the gun against a vertical wall, butt on the floor, and then measure the distance between the wall and the top of your front sight. Down pitch should be at last 2 1/2 inches for most men. More than 3 inches is not uncommon.
I have found that with the correct down pitch, I can also then shorten the LOP on a gun to under 13 inches, and still mount and shoot the gun well. I stand a little more than 6 feet tall, and weigh over 250 lbs. I have the barrel chest problem, but even with my long neck, I have tried some antique shotguns with LOPs of 12 1/2 inches and DPs of 3 1/2 that came to my eye very quickly when I mounted the guns. And, to my surprise, the fingers on my shooting hand did not feel like they were being cramped because the trigger was so close to my face.
Finally, remember that a gun stock is mounted to your face, so that it is on the side of the face, and not under it. If you are laying your face down on top of the comb, you are going to hurt yourself when that gun goes off. You are also not going to be looking out of your eyes normally down those sights if you lay your face on the top of the stock. That is not good for your eyes or for accuracy. I find that some stocks have combs that are too high, and that is why the shooter is having to lay his face over the top of the stock to get his eye low enough to see down the sights. A stock fitter will measure the distance between your pupil and the bottom of the cheek bone to determine the proper height at comb measurement for you. Again, the stock should be at the side of your face, with you standing, and holding your head sraight up. You mount the gun to bring the gun to your face, and not your face to the gunstock. This usually results in a stock that has more Down Pitch than the shooter has had in other guns, and it may also allow him to shorten that LOP, too.
