I shall try to answer your question. redheart feels that the drawing of the Hawken rifle will produce a rifle that is too delicate/fine to be a true Hawken. He bases this from the drawing itself, that appears to have a rather thin barrel for a Hawken. To me, the drawing has a barrel that is only at most, 7/8" across the flats, where rifles of this style, from the Hawken shop, have barrels in the 1" AF range. If you were to build the rifle according to this plan, using the drawing exactly, you might have to settle for a small calibre rifle. I disagree with him that the rifle is too slender. I have heard other students of these rifles describe Jake Hawken rifles as resembling what we refer to as Southern Mountain rifles in their dimension and style. Certainly, there is no extra wood left on the stock, particularly along the forestock. I submit that the stock is dressed down to about 3/32" or 1/8" along the sides of the barrel, or maybe a little less.
What will be most helpful to you as a builder, is to learn who drew the plan using what rifle(s) for their information. That will give you the opportunity to study the original rifle and or images of them, yourself, to confirm or reject whether the plan is accurate. Perhaps a phone call to Dixie Gun Works will answer some of your questions, if no one here comes forward with information.
Having never had an original Jake Hawken rifle in my hands, and only these plans for reference, and the desire to create a viable replication of one of Jake's rifles in say .50 calibre, I would go ahead and start with a parallel or gently swamped barrel that is 15/16" or 1" at the breech and between 38" - 42" long. Use barrel slides/keys and loops to secure it to the stock, and make the rifle as thin and delicate as the plans call for. I'd also place the front barrel tenon and slide abut 4" back from the muzzle...I don't see where the artist has placed his front keeper. It is correct to have a parallel sided plug tang with a pointed or circular terminal. I feel that the drawing of the trigger guard is fairly close to correct but the scroll at the rear might benefit from a curl that extends down into the scroll. I don't like where the artist has placed the second butt plate screw...I think it should be about 1 1/2" up from the toe, but again, not having had an original in my hand, I might be all wet.
This sheet of plans may be of great benefit to you in your build but I encourage you to find out as much as you can about the nuances that make a Hawken rifle, as you go along your build. Acquiring a set of appropriate parts comes second to education. And best of luck. I wish you joy in your build.