There were 3 teams that
(1) Had a 17-5 record.
(2) Won their conference.
(3) Did not win their playoffs.
1 of the 3 promoted.
So you not only need a good record, but you also need to win your conference.
A large number of the extra promotion spots were because there were quite a few D.IV leagues that were mostly bot, and had a bot win the playoffs. There has been a lot of growth in the USA, so many of the leagues will have a regular champion. The cutoff for the extra promotion could go up a couple more games.
If you can win 20 with your PGs and Cs swapped, go for it.