look at terry philips post close to the bottom of his post.
http://moreliaviridis.yuku.com/reply...3#reply-134723
more on perch size
http://moreliaviridis.yuku.com/reply...9#reply-133209
http://moreliaviridis.yuku.com/reply...8#reply-117928
those are a couple that i found really quick. also look at john romano's findings. he has been using true natural style set ups with multiple perch sizes and has found that the animals are choosing smaller sized perches.