Today I used the tube ring of my Canon 100-400mm and it does not work very well, it actually slided when we're observing, but as expected, there is no room for the scope to drop out. And after the observation, I got a new ring which is a third party ring for the Canon 70-200mm f2.8 and it does not fit well. Again, this is expected and I placed some padding material and now it's very firm unlike this morning. This ring will stay with my Ranger and the ring for the Canon 100-400mm can be returned to its intended partner :-)
Now the transformed Ranger is ready for any serious battle under the starry sky or sunny sky!