Wodent wheels are brilliant hung from the bars. I've only done it from the top but I've seen it done from the side as well. As SKB says, I wouldn't do it with a Trixie wheel because the wheel could fall off the stand easily, but Wodent wheels don't have that issue due to their design. The spin much better upside down I reckon and you have space for substrate underneath them. Have attached a link to the Transoniq site that has lots of examples of how to hang wodent wheels, either in cages or tanks.
The new Silent Runner wheel comes with two square plates for attaching it directly to the bars of the cage. I have it and it's very stable and doesn't bend the bars because the square plates are big enough and take the strain.
Scroll down for photo examples
Wodent Wheel Tidbits
This is my Silent Runner attached to the bars (fits 7mm bar spacing ok)
This is probably what Molly was describing about threading the wodent wheel stand through - Charlie had the Wobust wheel hung from the top for a while. I found 3 cable ties in strategic places worked better than lots of cable ties and it was really sturdy
