About Balance: I once had the privilege of examining an Original English DBL 12 Gauge shotgun, made by the Tower Armory in London, dated 1776. It had Brown Bess sized Flintlocks, of course, and there was a drilled hole in the front of the trigger guard for a military style sling swivel. The gun had 36" barrels, and balanced perfectly on the forehand. LOP was ONLY 12.5 inches, but the Drop was more than I had on any gun I owned. I didn't write down what the Drop at Comb, and Drop at heel, nor did I record the pitch measurements( DARN!) So, I can't give you those numbers.
BUT, I can tell you that the Brass Butt Plate on this shotgun was thick, and almost 3" wide at its widest part. Altho I did not DARE try to remove the butt plate from the gun, I am sure that it was cast, nor forged, and I suspected that there may have been additional weight in front of the plate to help achieve that balance with those two barrels. I stand a little over 6' Tall- closer to 6'1", and that gun came up to my shoulder and eye like it had been made for me- not someone over 235 years ago.
You won't want a shotgun with a "too-long" LOP- as it will catch on your armpit as you mount the gun, and the gun will be stretched out even further from you so that balance will be of no use to you. IMHO, I would recommend staying with your normal LOP, and adjusting both DROP, and pitch, to make it fit you. Don't forget Cast-off, as that always helps a shotgun point targets faster. Then, if you have need of more weight, cut a hole in the stock under the butt plate, and add lead shot, or weld a chunk of brass to the inside of the butt plate, to give you the needed weight.
Because you live on, and hunt Kodiak Island,(Alaska) where large bears are always a concern, I think you know exactly what caliber a barrel should be for your kind of hunting. :thumbsup: :thumbsup: