The more pins the merrier! And in this case, the more players you can handle at one time, and the faster your rounds would play.
I’d encourage you to plot out your tourney time based on past tourney duration information.
Go back and look at the time it took for a 19-player single-player double elimination on 4 pins. Was it really just 2 hours?? If so, that’s remarkably fast for only 4 pins available, unless all your pins are 2" flipper luck-box pins like Slick Chick. Find the bracket you used, or if not available, pull up a sample blank bracket from the internet of what that looks like, and count the total rounds that had to be played (start with the lead-in round and the first full round of the winner’s bracket, and then count the Loser’s bracket all the way to the championship match). Then divide your total tourney duration by the # of rounds, and that’s your average time it took per round.
Next, go to the IFPA site on TGP Guide, which tells you how many “meaningful games played” your tourney will have for a 24-player, 3-strike tourney (this tells you the estimated # of games that the eventual will need to be played by the eventual tourney winner). Multiply this # of games by the duration per round from above, and voila! There’s your new tourney duration estimate.
With only 4 pins, if you go beyond 24 players, then your intial rounds will take approx 33% longer, because each round will involve 4 groups of head-to-head matches instead of just 3. (For the first 3-5 rounds: 24/2 = 12 matches per round. 12/4 pins = 3 sub-rounds because people are waiting their turn to play a match.)
Last, keep in mind that if you’ve got a lot of the same repeat players between tourneys, and if it’s the same 4 pins, the players will naturally get better and better at the pins you’ve had on location – as they play the same pins from prior tourneys or from all the quarters they’re hopefully dropping in those pins during usual business hours.
In addition to the rules at PAPA.org, they’re also a great resource on pin-specific notes as it pertains to setting them up for tourneys. And in some cases, noting which pins are not appropriate for certain types of tourneys, depending on skill level.