I found a pump belt restrictive if I tightened it and didn't hold the pump in place if it was loser.
The best option I found was the clip it to my leggings but had to move it depending upon the exercise. For most cardio, it was ok clipped in place. But for weights and stretching, I often had to move it around. The clip was easy to move.
For cardio exercise, I was happy to remove it most of the time because I would reduce or suspend the basal to avoid a hypo. However, other exercise such as climbing caused my levels to rise.