Maybe Chepi can help you a bit by writing about Chepi's experience's until Chepi found one that suited Chepi.
At first Chepi thought silicone or plastic would be easier to wear. But as things turned out metal devices are much better, they hurt less and are easier on the skin. Chepi can wear the metal device without lube while silicone or plastic devices without lube result in stickiness, high friction and subsequently in chaffing.
Another mistake was to use to large devices. The guideline should be the smallest cage (1. by length and only 2. by diameter) that you can get your limp cock in combined with the smallest base ring that still moves comfortably (without any constriction). For Chepi that resulted in a Bon4m small with a medium sized base ring, that Chepi modified a bit to get achieve smoother edges of the base ring + a lockable screw (see
http://www.getdare.com/bbs/album.php...ictureid=58239)
Woof Woof