Bobski:
I'm 5'6", so this may not be of much help. I've owned and shot two different Model 21s, both double trigger (which I prefer on a sxs), splinter forend guns, 28 inch barrels, one with extractors and one with ejectors. Both were 14-1/4 inches over a Winchester butt plate, which I think was the standard factory LOP. Both weighed less than 7-1/4 pounds, which is light for a 12 gauge Model 21.
I suspect both would have been too short for you, given your height, so you may need to add a pad regardless of the setup you find. If you want a true field gun that can double as a target gun, either of these would work fine. In addition, you will find that the double trigger/splinter configuration sells at a discount to the standard Model 21 with single trigger/beavertail, which for me was a nice bonus.
