I had a look through the membership list to see if there were any members who have converted or are converting a Westerly Centaur, and there are at least two, (Obelix and Tamlin). Sakari can go from the Home Page to the "Members' Area" and select "Members' Boats" and from there, search Obelix and Tamelin, and the email addresses of these two members. This might help.
Laurent Giles and Partners design, over 2,500 built and plenty of information on the internet regarding this design. I guess the approach would be to consider the accommodation layout and decide where a free-standing mast would best be placed, which will be some place through the forward cabin top - and this will in turn decide the type of junk rig which will suit.
From this review (click here) it seems the boat is a somewhat high-wooded, commodious, fairly shallow draft and beamy vessel, so no surprise also to read that it tends to develop weather helm fairly quickly if not reefed early - and it is not particularly easy to go to the mast to reef - all suggesting that it may well be much improved by converting to junk rig.
It might bbge possible to make contact with the owners of Obelix and Tamelin. Many (probably most) members do not follow the forum, and won't have seen Sakari's request - but presumably will respond to an email.