Agreed. I wish I'd seen Khalid's response earlier.

Using either a "guide" or "lim" will result in the same shape. Two solid arrows that are offset from the line, lateral to the line.

Using 'x' and 'z' restraints, or derivatives thereof, e.g. x[1,0,1] will result in hollow arrows (like the y arrows) that are attached to the line.

The benefits of "guide" and "lim" are a) they are always lateral or axial with the pipe without additional input, and b) they are easy to differentiate in the lists.

It seems the best of both worlds is to use "guides" and x/z for limits. At least for our older version of CAESAR.