Opponent matching is so poor that it's discouraging me from playing Arena Mode.
In Puerto Rico, inexperienced players tend to make naive moves that can disproportionately favour the player who goes immediately after them. That gives the seat order a huge influence on the outcome - which doesn't make for very fun games.
PR's "balanced" mode is there to help balance out seat-order bias problems with the game. Adding inexperienced players into the mix undoes all of that.
In "Simple" games I usually set the player level to Good+, or Strong+ - which is enough to weed out the players who really don't know how to play. I've not found anything in "Arena" mode that guarantees me decent opponents. The "Opponents' level" chooser is just weird: If I set "I never want to play with..." to everything except "My level", it makes a table that *only* accepts "Average" players!! I'm "Expert", so that's very far from what I want.
CONSTRUCTIVE SUGGESTION:
I realise that you want to emphasise the seasonal ladder aspect of Arena play, so restricting players by ELO is against the spirit of that. My goal is to exclude players who don't yet know how to play the game. You already do that by setting a "100+ ELO" barrier for entering the Arena. In PR at least, players with 100 ELO almost certainly do NOT know how to play the game.
I suggest that you make this ELO barrier vary from game to game. Set it to AT LEAST 200+ for Puerto Rico.
This will force new players to learn the game in "Simple Mode", before they can enter the Arena.