What is a good approach to conduct a round robin event for 20 players in order to select top 6?

Question

I need to have a selection event for 20 players to select 6 players for a team. Plan is to have a round robin event since it is fairer compared to a swiss event. Then each player will have to play 19 games. Also the plan is to have 1 hour for each side without increment.

If I breakdown rating wise
1800+ count = 4
1800- count = 16

1700+ count = 8
1700- count = 12

1650+ count = 9
1650- count = 11

1600+ count = 10
1600- count = 10

1500+ count = 15
1500- count = 5

What would be a good approach to conduct this event? Should I have all 19 rounds? Or is it better if there be 2 rating group tournaments where selected players of lower rating stage get promoted to higher rating stage tournament.

This sounds like an opinion based question, but I would appreciate if someone help me with some insights.

Answer 1

To get the fairness of a round-robin without quite so many games...

First, separate your players into 2 groups of 10. I'd suggest making the groups each have a good mix of players rather than having a "strong" and "weak group, although that's not strictly necessary. Have them play a round-robin in the group. Top 6 advance. This part will take 9 rounds. (If someone can't get in the top 6 in the smaller group, they weren't going to get top 6 overall, so it's safe to eliminate that player.)

Now you've got 12 players left. Have them play a new round robin - BUT - if any players had played in the previous round robin, you use that result instead of having them play again. That way, instead of this part taking 11 rounds, it will only take 6 (since everyone will have 5 games already played.)

9+6=15, so this only takes 15 rounds instead of 19, and nobody is going to get eliminated just because they faced stronger opponents.

Answer 2

A round robin is not that much fairer than a Swiss. There are lots of solutions you could try and, as you say, it is pretty much a matter of opinion. I would suggest a 5 round Swiss followed by a 5 round, 6-player round robin where the 6 players in the round robin are the 6 players finishing in places 4 through 9 in the Swiss. Then pick the first 3 in each tournament.