<font color='#0000FF'>Hi Aclivity
When I dive my singles rig I don't use a pony, don't see the point to be honest if you have decent regs and a decent buddy.
However if forced by gunpoint to use one then I would sidesling it.
If you're planning to dive below 30 mtrs then its better to save for that twinset as that is your best form of redundancy in my opinion.
http://www.dir-uk.org/equipment_guide.doc
Above is an article which changed my whole view on kit and pointed me in the direction I go now. Page 27 mentions Pony bottles
HTH
WL