@elizabethtasker
You'd probably want the cage to be only slightly taller than the underlying cylinder, while a fair bit wider - imagine the view direction rays coming in radially and horizontally for the curved part of the cylinder, rather than increasingly from above or below at the top and bottom...
(I rarely use any manual cage stuff, letting Substance Painter or whatever do that automatically. Then there's the fun of dividing meshes into sections, so stuff doesn't get in the way...)