If you unzip the bag from the base, it should be engraved on the base what bikes it fits. Looking at the picture you have, that bag is NOT for an 1100. Not saying you can't make it fit an 1100, but......
The side straps go down too straight. The 1100 Tank bag side straps also will have formed flat steel hooks that will connect with mounts that come out from between the tank and side panel.
The rounded, bent wire hooks, if you will, are intended to clip on the bottom seam of the gas tank as you have done, but this design was intended for the K75's and 100's, but maybe just not the LT/RT variation because of the side panel gap between the panel and tank.
Will also delete your other duplicate post.