It is hard to answer a question like that for you. If you really want to get something off your chest and have taken the time to consider the outcomes and still want to do it. then do it.
Do you have expectations attached to having your say?
Are you looking for an apology? It bears some consideration before taking the action.
I never did contact the single OW.
But I have read many threads on this site where posters got information from or had their say to the OW and were glad they had the experience.
It really is up to you.