I find the dynamics of the 21s to be excellent, similar to how I feel about Perazzis. Weight between the hands with a relatively heavy receiver, well struck and light weight barrels.
I distinctly dislike vent or raised ribs on any guns, especially side by sides. I would get the matted rib (mine was a 12 gauge matted rib skeet gun).
Also, I sense you are considering ordering a new gun. If that's the case, I'd consider getting your dimensions pretty well set with a good fitter over some time (not a one or two hour "fitting").
I tend toward longish barrels, and I'm nowhere near as tall as you. My own observation as a long time observer and shooting instructor is that most folks shoot guns shorter than they should, but that's dependent upon alot of things that can't be prescribed without direct one on one interaction. Consider 30" barrels, and also consider more difference in chokes than only one step (such as WS1 and Mod or IM), unless you are a serious skeet shooter. Another factor is whether you will use this gun exclusively for target shooting, or a mixture of game and targets.
I also like heel and toe plates, or a skeleton butt plate; I think a pad on these guns is like lipstick on a pig.
In the Model 21, I'd consider either the 12 gauge or the 16, as these tend to feel much better to me than the 20s (which seem a little dead in my hands, compared with these). These guns are heavier than they need to be, for game guns, as their strength lies in the massive action and long water table.
In terms of placing a special order, I'd be very careful, as sometimes the custom route can be very disappointing if the maker and customer aren't in 100% communication. I believe I would be patient, watch the used market for something that comes close to my requirements and buy a genuine Winchester.
