Welcome George!
I've built a ton of shoulder holsters over the years, but never have built the type with the spring. I don't normally carry with a shoulder holster with my 1911 or 1911 Commander, but when I do I use the horizontal type with a thumb break and a couple of mags under the opposite arm help with the balance a la Sonny on the old Miami Vice. You can see a bunch of this type here:
https://www.google.com/search?q=hori...w=1024&bih=454
If you don't have a lot of luck in your quest here I'd recommend checking out the Leatherworker forum where a bunch of holster makers visit
http://leatherworker.net/forum/index.php
Also I do have buried somewhere in my plethora of to do projects an older well made holster of the type you're looking to make without the straps which would be easy to figure out and even replace. If you have no luck finding help drop me a note via the forum or email and I'd be glad to send it to you (as soon as I find it!) - might as well somebody got use out of it...