After many years of lambing on large farms, I never managed to keep a spoon in with string tied to fleece!
I preferred the stitch, but it does need constant attention to make sure it doesn't tear the ewe when she tries to lamb if you haven't cut it. I also found the harnesses really good.
If I was putting in spoons, I made a makeshift 'harness' to tie it to with baler twine, ideally the thick stuff, if not then double/triple thin stuff to make it less likely to dig and rub the ewe.
First step was a good loop that goes round the neck, tied onto itself so it won't slip tighter when attached to the other strings.
Then a string tied to the middle of the loop, going down the middle of her back.
Finally, a loop round each back leg, tied to the string in the middle of the back until reasonably tight.
Then I could get the strings on the spoon to tie somewhere that seems the most natural angle either on the back leg loops or the join in the middle of the back, depending on the shape of the ewe.
Hope that helps someone
Suzanne