[Freesurfer] Xhemi results

Dear Doug and FS experts, I am trying to use Xhemi tool to study asymmetry in the brain. I have done the exact procedure you mentioned in WiKi for a group of 40 controls. 1) Is lh.lh-rh.thickness.sm00.mgh the stack of voxel-wise cortical thickness difference between left and right hemisphere of each subject? 2) If yes, shouldn't I see the similar mapping by overlaying this to lh and rh? (tksurfer fsaverage_sym rh inflated -aparc -overlay lh.lh-rh.thickness.sm00.mgh) 3) How do you interpret the result after analyzing within one group? ( tksurfer fsaverage_sym lh inflated -aparc -overlay glm.lh.lh-rh.thickness.sm05/osgm/sig.mgh) 4) Is there any way to look at the results through the brain per slice and also the whole brain?