Hi Chris,
I have a 14.5" SDM scope (literally identical in design to Obsession).
The adhesive patch kit is probably provided to help stop the sling from sliding off completely. My sling was on the verge of coming off with only a few mm hanging on the edge of the mirror
. I only realised this as I just couldn't get collimation right. After speaking to Peter Read (builder of the SDM) we worked out the iproblem.
If it happens to your scope, simply put the scope in the upright position and using your fingers pry the sling down until its flush with the mirrors edge.
After adjusting the mirror again so the sides are evenly positioned, he suggested to just place some gaffer tape on the sling to the back of the mirror in a couple of spots to prevent it from sliding off in future. Peter thinks it may have happened with the new sling stretching a bit under tension giving it a bit of slack. After tightening the bolts (left/right) the sling is relatively taut and I haven't had an issue since.
I was pretty nervous when I saw the mirror precariously hanging by a mm or 2, but the problem is not really as bad as it looks after Peter explained how things worked from the back of the scope.
I remember that night quite well and learnt the entire collimation process over the phone. Credit must goto Peter Read.
Thin double sided tape is another option between the sling and the mirrors edge. Even though the tape is not needed, it does give me peace of mine.
