Sand Hill Preservation does breed to SOP. Their goal is to preserve genetic diversity so they do not cull for minor imperfections. You can get a group of these and do your own breeding and culling. Their stock will be superior to any of the commercial hatcheries have to offer. I have bought many breeds from SHP and was never disappointed. I do not show so imperfections do not make phase me. To say the least, their stock is robust.
There are not many people with the passion and dedication to preserve heritage breeds that the Drowns display. I applaud them.
From there site:
1. All breeds within the APA Standard are selected to those standards. We do, however, not discard a bird from our breeding program for minor flaws, such as an extra point on a comb or a slightly off color eye, if the bird has other desirable traits. Our goal is to maintain genetic diversity and all defining characteristics.
To me that is not breeding to SOP. If you do not discard those minor flaws, you pass them on. That said I admire what they are doing to preserve rare breeds.