NavList:

Centering the scope shouldn't effect anything except that view through horizon mirror might be blocked somewhat on one side, only effecting the brightness of one image and possibly some aberrations, which should be small in a good scope.  Even the index error shouldn't be affected.  If not really bad, either lateral decentering or angular decentering should not affect the readings or index error.  As long as the filters aren't changed, wedge should be accounted for in the index error.

Someone correct me if I'm wrong. Might be some practical problems, but that's how I see it from the 'theoretical 'angle'.