I have a 93' 31 active thunder
5400 rpm
1.5 gear
24 pitch Bravo's
67.5 GPS
@17% slip.

Tried multiple trim positions kinda found the sweet spot I think. To reduce slip are my only options to step up to 5 blades?.

Any advice is appreciated

Actually your slip is only 14%-15% since the 24 B1's are more like 23-23.3 pitch.
If the props are tired or you are over trimming the slip will go up too.
Adjusting or face lifting the props will help.
Let us know if you wish to do that.

Brett