I agree that maybe more overhead cover would help him feel less nervous. I also think maybe he wouldn't feel very secure with the long bendy bridge higher up - they seem to feel more secure with something stable and solid to walk on - again partly depends on the hamster. If you had some overhead cover also you could move the coloured knot toy underneath it so there's more room on the shelf and more floor toys.
A couple of options. I have two rat sputniks and do have an extra shelf at the other end.
Prior to this set up I had a large flat roofed house at the opposite end to the shelf the wheel was between them at the back). This doubled up as an extra shelf but also gave our hammy a big dark house to feel secure in. I'll add the photos in case it gives some ideas.
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