I tried Aruns wheel on the side of the cage but the rattling was awful (borneo xl). Kashis is also on the side of the cage (barney) and is completely fine.
Prob. going to put Robins silent runner on a shelf. Nice idea AP.
Attaching the Silent Runner to the cage is great! It fits so well and has a large spacer so it sits proud of the bars and doesn't catch on the cage base. Doesn't rattle at all