Did you hang it from the top bars? I find them ok - in fact they're quite hard to attach to my bars as they're 7mm.
This is how I have Newt's sputnik
You can put them upside down on a shelf - I always worry they'll slide off the shelf with the hammy inside though! They're quite light and can be pushed around or jiggled to move around. Might be better upside down on the substrate.