Today we build to a 'norm'. A norm that is based on what? Dixon's Fair? John Bivins?
At the Landis museum, there is a latecomer, the 'Musician's Rifle', which is a robust early gun. On the sideplate view of the gun, the wood nearly comes up to the top corner of the side flat of the barrel. That would not fit today's 'norm', but it is certainly beautiful, and it works for this gun.
In my opinion, all the rules are subject to question. If you can put something together, and it's beautiful, you've pulled it off. Height of wood, forearm thickness, lock panels be !@*%&@. Make what WORKS, visually and mechanically.
This does not mean careless, it does not mean thoughtless. A gun, a painting, a woodcarving, all have to be deliberate acts.
I will look at a rifle/fowler, and immediately determine if I like it or not. It's not something I even have to think about, or be talked into liking it. I either like it or I don't. It's about materials, form and finish, primarily, and embellishment are complimentary treats.
The foundation of the gun is the FORM. That is what I see from a mile away. I am immediately am drawn or disinterested. Form of the gun is the foundation upon which the rest of the gun is built. You need to spend the time getting the form to where it pleases you. Don't rush this stage. If you're not sure what you're doing, build many guns. You will figure it out, if you're driven to do so.
The finish is so often neglected, but it's what the beholder sees, even before touching the gun. The finish is SO critical to the gun. To develop a good finish, and an appealing finish, takes time and artistry. Again, here is a place where 'norm' can creep in. Myths like: 'Guns should be finished like Judd Brennan's, or Allen Martin's, or Bill Shipman's.....' have no place in your build. Again, the finish is such a personal thing, one must determine for themselves what finish they want to use. Want a 'new' look? Used gun? Old, worn beaten gun? They all have their appeal. You must decide what you want to evoke, and try your best to achieve that look. It ain't easy. The finish is an art all unto itself.
With all this blathering, I forgot where I was going.....