there is a easy way to find out what polartiy it is when using twister.
By default, the splitter/coupler out provide is V-pol. like following.
The Twister has to marks, one shows V and one shows H.
All you need is to make sure the mark is aligned with the mark on the coupler or split. Then you know you are on V pol or H pol.
Here is example of V pol.
here is example of H pol.
Regards
Allen