LOP for target guns is far more flexible than for field guns. Shooting premounted, it's relatively easy to adjust to a significant difference in LOP. Mounting in the field, in response to a surprise flush or even over a point . . . too short isn't so bad unless you're bashing your nose, but too long will usually result in catching the gun somewhere under your arm or on your clothes, and it's bye bye birdy.
Bob, I think I recall reading somewhere--maybe Batha--that dimensions for the smallbores should be different than for 12's. Especially so, I think he said, for 28's and 410's. I'm fuzzy on it, but I think it was less drop for the smaller gauges. Don't recall whether there was an LOP difference. SxS vs OU, as long as both have the same number of triggers, I wouldn't guess there would be a lot of difference.
