What style are you building? John Rupp and John Moll patterned guns (from the Central Lehigh county style) are the most often built. I also tend to consider them the trickiest to get right. I strongly suggest you get a copy of the Kentucky Rifle Assn Disc # 10 and study all 20 of the guns on it. Every nuance, and every detail. Not just the style you are building, but the others too. Look at what contemporary builder Allen Martin does too.
With that heavy of a barrel you're surely going to want to keep that web very thin, like 1/16" in the back, and 5/32" in the front. Side flat coverage should be about 30%-35%. RR coverage around 1/4 -1/3.
Just about everything on these rifles is different from just about every other style. It's really really easy to mess up the architecture. That's why it takes most builders about 4-5 tries at building one before they feel they get it "right".
One thing to be aware of, is that, unlike more popular styles like Lancasters, there are no static curves in most of the architecture. They are continuously evolving--getting tighter or looser as the position changes along the stock. For example; look closely at the toe line curve radius along its' entire length for (ignoring the double radius curve under the trigger guard of the Rupp for the moment). You will see that it starts out loose near the trigger guard, than gets tighter and tighter as you approach the butt plate. The top line of the wrist needs to be high. That's what I think is the biggest cause (wrist top line being too low) of a lot of contemporary Lehigh builds' architecture being "off".
Another very common mistake (with the Rupps and Molls) is to cut in the double wrist radius curve too deep, and /or of a static radius. That curve radius should be subtle, and have an evolving nature to be "right". That (static radius) results in architecture that doesn't quite "flow right" in the butt and through the wrist. Study the disc on those guns very carefully. It's a VERY subtle profile. It has to "fit right" in it's curve radius with the relationship with the comb nose, and comb curve radius. It's a very subtle thing. When you hit it, it's beautiful. When you don't, the result can look kinda clunky. By that, I mean that your eye should be naturally drawn to "sweep" along the length of the rifle in a visual manner giving the gun a graceful look. When there are distinctive areas that your eye tends to want to stop, (usually that's in the transition zones) and the curves appear to change direction abruptly, that's what I mean by "clunky".
So look at lots and lots of guns from all the resources. And, as important, look at them very critically. Try to identify what almost ALL of these guns got wrong in their architecture (and they all did to some extent) , and, what they got right.
The shape of the cheek rest rollover and concave portion of the cheek rest makes all the difference in whether the gun will be a cheek slapper or not. How will your head be aligned when you mount the gun? You want it upright and facing more forward than on other styles, with a rounder comb top than some other styles forward of where your cheek bone lands. That will let the gun kick out of the way and your cheekbone to slide off more when it's coming back rather than rise up to smack you.