My single engine 525SC boat was about 17-18% slip with a tweaked 26" Barvo 1 prop.
When calculating slip for a Bravo prop, subtract one of pitch. The stamped pitch is higher than actual pitch.
Your boat is a lot lighter than mine was though. Mine was a full pleasure boat and probably around 5400lbs. I also had a notched transom with a 20.5 X dim and ran a 3" spacer to lower the propshaft depth.
You may want to try a 1/2 inch spacer.