anchor.diff:  
       case(41) ! RF Multipole
         ktrack(i) = 66
  +
       case(43) ! X Rotation
         ktrack(i) = 68
  +
       case(44) ! Y Rotation
         ktrack(i) = 69
  +
       case(45) ! S Rotation
         ktrack(i) = 70
   
  
positive.code:       call thck6d(nthinerr)
      end if
    else
      if((idp == 0 .or. ition == 0) .and. .not.do_coll) then ! 4D tracking (not collimat compatible)
        write(lout,"(a)") ""
        write(lout,"(a)") "TRACKING> Starting Thin 4D Tracking"
        write(lout,"(a)") ""
        trackMode = "Thin 4D"
        call thin4d(nthinerr)
      else
        if(do_coll .and. (idp == 0 .or. ition == 0)) then ! Actually 4D, but collimation needs 6D so goto 6D.
          write(lout,"(a)") "TRACKING> WARNING Calling 6D tracking due to collimation! Would normally have called thin4d"
        endif
        write(lout,"(a)") ""
        write(lout,"(a)") "TRACKING> Starting Thin 6D Tracking"
        write(lout,"(a)") ""
  
negative.code: 
    nthinerr = 0
  #ifdef FLUKA
    napxto = 0
  #endif
    if(lbacktracking) call aperture_backTrackingInit
  
    if(ithick == 1) then
      if(tr_is4D) then
        write(lout,"(a)") ""
        write(lout,"(a)") "TRACKING> Starting Thick 4D Tracking"
        write(lout,"(a)") ""
  