It's been a while since I've spent any time with this project, had a weekend away from work and some down time , a chisel a scraper and a rasp...   
Don't have the breech block quite fit in yet but it's coming along, I'll share pictures later.

Bob,
The reasoning behind the tang is it provides a point for the breech block's toe to lever against.  If one was to try and broach this surface in the action the Ballard would become even that much more difficult to make...  I believe Vall's comment that the Ballard is weaker but neater is a very valid comment.  The Ballard has two points - the toe and the back that the lever and link cause a camming action for lock up.  At the same time, the short angled section has to make contact to serve as a recoil surface.  Getting these to all come together at the same time is quite a process.

The size and shape of the tang also help support and align the stocks on Ballard actions. Unfortunately the large size near the receiver also meant the wood was thinner, so the common "Ballard cracks" are the end result of the design after 100+ years of use.
When I build new stocks for a Ballard I relieve the inside tang area enough so I can coat it with Acraglass, or bedding compound, to help support the inside of the stocks in hopes of avoiding the cracks. But since they take so long to happen, no telling if my method will work in my lifetime?

I've encountered several arguments from folks that tell me what I'm posting here is totally incorrect and that the breech face is what makes the lock-up.  What I have discovered is when the lock-up is correct, a head-space exists, I prefer .002-.003" in most cases (pun intended) - the barrel doesn't make contact with the breech block.
In my attached sketch, layout of the surfaces is the challenge.  One thing I have discovered in studying several Ballards, mostly Marlin's and a couple of Cody's, the point of contact that the majority have at the back is a very small point where the recoil lug and the back meet.  I do have a very nice vintage #9 forged receiver that when I checked the contact point on this, the recoil lug area made full contact but the contact between the breech block and the action at the "back" point, was almost 3/4" long.  This rifle closes up and snaps very nice.  I attempt to make all of mine follow this model now.
Vall, 
I agree with you on the use of acraglas.  A couple of my builds I chased wood to metal contact - and succeeded.  As they aged and are used there are some issues developing.  I now use a thin layer of glass and they seem to be as tight and secure as the day I did the bedding job.  Glass is inert, while the wood is in a constant state of change - my blanks were still 20+ years old but still have some movement...
Greg

Greg, we have had some email conversations on the lockup and I still have been a bit confused.  The light came on while looking at the pictures and have a much better idea on it now.  Thanks.  Too bad there is not a cutaway of a Ballard that would show the lockup.
Bob

Vall, that is the way I had always done it.
Greg's comments were like a lightbulb, saying "hey, you dummy".
Chuck

I've made a little progress on shaping the wood and last night before I called it a day, I threaded the barrel blank and have it fit up.  This is another Shilen blank, 1:10 ratchet rifling, 4 groove for the 22rf.  I'm going to turn the barrel to a slight taper full length round, except for a short Rigby flat on the top at the receiver end.    I've pondered leaving a lump at the muzzle end to elevate the front sight slightly and make a small integral ramp... somewhere I have a Beech style windage adjustable front that may look good here.  Another photo shows a base (Robbins style) with my intentions.