Sorry if a little late to the party, but I just discovered this thread while looking for centers myself. Link to Arendal 1723 Monitor/Center tested polars (1723S will be of little difference as its the same toppled MTM design with smaller woofers):
https://www.audioholics.com/bookshelf-speaker-reviews/arendal-1723/conclusion
Really wanted to like Arendal, but the imo shady practice of only showing vertical polars for their centers, as well as stating in writing to me they don't have horizontal polars for their centers (unbelievable coming from a company that actually has good engineering)...well they have likely lost my business for a full HT setup. 15-20 degrees just doesn't cut it for me, as reflected sound matters too.
AH constantly pounds on them they need a real 3-way center lol.
Edit (additional info):
Maybe they could at the very least move the tweeter up, and get the woofers closer together. New box/crossover tweaks/sku needed, but at least there would be no additional driver costs.