Free Agent Pool Size

https://www.pennantchase.com/league..

MLB The Glory Years ran smoothly through the 2000s with minimums set at
AB: 35
IP: 14
Rosters: 32 (Cut to 27 during the off season)

The Free Agent Pool wasn't huge but it was big enough that teams could pick up a needed bat or fielder during the season.

We recently rebooted the league back to 1969. Roster sizes were reduced to 30. 4 man rotation was implemented. Everything else remained the same. After the supplemental draft that returned rosters to 30 players, the free agent pool was virtualy nonexistent.

I have never played a real stats league in the 1970s. What am I doing wrong?

I can only 3 solutions or combinatinos there of, to increase the free agent pool.

1. Decrease roster size.
2. Decrease stats.
3. Import players from another era to be used as filler players.

I am looking for suggestions from experienced owners, as to what they would expect from a league during the 1970s.