ok, i’m pretty good at doing skeletons, but i’ve never made a skelton yet than can use the paste flipped function.
how do you create an armature so that it can be flipped. It must be to do with the axis you create it in.
-Luke
as far as i remember you just need to get the bone names correct. Take an arm as an example:
fore_arm.R <= upper_arm.R <= spine => upper_arm.L => fore_arm.L
As long as the bone names are the same (case sensitive) with the right extension (*.L or *.R) then bone.L will map to bone.R
just select the bones you want to copy the pose, ie just the arm bones. If you select the spine as well i don’t think it’ll do anything but sometimes it seems to mess up.
also, when mirroring bones using Ctrl+X it screws up the bones ‘normal’ (sry, don’t know what the equivilent is with bones) this messes up the rotations when copying poses. I think you can solve that by Ctrl+N to recalculate, but i’m not sure about that.
hope that helps, or at least doesn’t make things worse 
cheers
Piran