It is possible that MikroTik considering a change of holder SXT/SEXTANT, so that it can be adjusted elevation without buying additional holders? That would be a great advantage over UBNT products.
For small angles you can use plastic cable ties around a pole to tilt a holder.
We are considering it.
Meanwhile, you can look at something like this: http://www.rfelements.com/products/brackets/nanobracket-sxt/