Clamdigger,
If you go back and read the entire article on the original SRF (that's where these pictures came from), I warned several times in the text
do not put a half turn in the sling because of the cant that it will induce.
The K31 quick detachable clip
will fit on the M1 web sling, and that's what I use.
You detach that end of the sling from the stock when using the loop sling in sitting and prone.
The K31 quick detachable sling clip will not fit on the M1907 sling because the metal frog of the US sling will not pass through the narrow loop of the Swiss part. However, you can modify the quick detachable clip from an M1 web sling to fit the sling bar in the K31 stock. That clip
will slip on the M1907 sling, and then the tail of the sling can be detached in the same way that the M1 web sling is detached.
Top: The "stock" M1 sling clip. Bottom: M1 sling clip modifed by bending and narrowing to fit the K31 sling bar. These "pictures" were taken in my pre-digital camera days: the modeling clay holds the parts on the glass of an ancient flat bed scanner, which took the "picture". These sling clips are available as a separate part from Numrich and others for a few bucks, so you don't have to cannibalize a complete M1 sling to get one to modify for this use.
The modified M1 sling clip used with a M1907 leather sling on a K31:
As I noted above, the Gew 1911 lower band
will fit the K31 and positions the sling on the bottom of the stock. The use of this part is contrary to CMP rules for "as-issued" rifles, however. At least one guy got away with it last year at Perry because none of the line officials was smart enough to tell the difference. Unfortunately, I was cursed with a conscience, and I can't do that: even if no one else knows it's wrong,
I know. For NRA rules, anything goes, as long as it's not unsafe.
Hope this answers your questions .....
Resp'y,
Bob S.